Add README note on recursive submodules
Add README note on recursive submodules

As libextobjc also contains submodules, git submodule add ... may not
pick them up automatically
longv2go/ReactiveCocoa,wangqi211/ReactiveCocoa,nickcheng/ReactiveCocoa,dachaoisme/ReactiveCocoa,ericzhou2008/ReactiveCocoa,leichunfeng/ReactiveCocoa,paulyoung/ReactiveCocoa,zhukaixy/ReactiveCocoa,Pikdays/ReactiveCocoa,jrmiddle/ReactiveCocoa,mxxiv/ReactiveCocoa,j364960953/ReactiveCocoa,Liquidsoul/ReactiveCocoa,liufeigit/ReactiveCocoa,luerhouhou/ReactiveCocoa,shaohung001/ReactiveCocoa,GuitarPlayer-Ma/ReactiveCocoa,jackywpy/ReactiveCocoa,chieryw/ReactiveCocoa,tornade0913/ReactiveCocoa,tonyli508/ReactiveCocoa,BrooksWon/ReactiveCocoa,eliperkins/ReactiveCocoa,dachaoisme/ReactiveCocoa,Remitly/ReactiveCocoa,Ray0218/ReactiveCocoa,zhaoguohui/ReactiveCocoa,nickcheng/ReactiveCocoa,OneSmallTree/ReactiveCocoa,valleyman86/ReactiveCocoa,zhiwen1024/ReactiveCocoa,zzzworm/ReactiveCocoa,ztchena/ReactiveCocoa,fhchina/ReactiveCocoa,yaoxiaoyong/ReactiveCocoa,CCOOOOLL/ReactiveCocoa,AllanChen/ReactiveCocoa,tonyarnold/ReactiveCocoa,Pikdays/ReactiveCocoa,ohwutup/ReactiveCocoa,loupman/ReactiveCocoa,ikesyo/ReactiveCocoa,DreamHill/ReactiveCocoa,AllanChen/ReactiveCocoa,hbucius/ReactiveCocoa,vincentiss/ReactiveCocoa,yoichitgy/ReactiveCocoa,Pingco/ReactiveCocoa,esttorhe/ReactiveCocoa,clg0118/ReactiveCocoa,ShawnLeee/ReactiveCocoa,zhigang1992/ReactiveCocoa,beni55/ReactiveCocoa,DongDongDongDong/ReactiveCocoa,add715/ReactiveCocoa,wpstarnice/ReactiveCocoa,sandyway/ReactiveCocoa,tonyarnold/ReactiveCocoa,jam891/ReactiveCocoa,natestedman/ReactiveCocoa,xumaolin/ReactiveCocoa,fhchina/ReactiveCocoa,huiping192/ReactiveCocoa,yangyangluoluo/ReactiveCocoa,335g/ReactiveCocoa,dullgrass/ReactiveCocoa,dz1111/ReactiveCocoa,imkerberos/ReactiveCocoa,OnTheWay1988/ReactiveCocoa,Liquidsoul/ReactiveCocoa,mtxs007/ReactiveCocoa,cstars135/ReactiveCocoa,juliangrosshauser/ReactiveCocoa,Eveian/ReactiveCocoa,shuxiashusheng/ReactiveCocoa,dskatz22/ReactiveCocoa,ddc391565320/ReactiveCocoa,valleyman86/ReactiveCocoa,icepy/ReactiveCocoa,taylormoonxu/ReactiveCocoa,leichunfeng/ReactiveCocoa,zzqiltw/ReactiveCocoa,jackywpy/ReactiveCocoa,200895045/ReactiveCocoa,Ray0218/ReactiveCocoa,FelixYin66/ReactiveCocoa,llb1119/test,tonyarnold/ReactiveCocoa,RuiAAPeres/ReactiveCocoa,yoichitgy/ReactiveCocoa,zhenlove/ReactiveCocoa,walkingsmarts/ReactiveCocoa,on99/ReactiveCocoa,chao95957/ReactiveCocoa,dz1111/ReactiveCocoa,leichunfeng/ReactiveCocoa,yangshengchaoios/ReactiveCocoa,wpstarnice/ReactiveCocoa,ikesyo/ReactiveCocoa,Rupert-RR/ReactiveCocoa,Ethan89/ReactiveCocoa,CCOOOOLL/ReactiveCocoa,pzw224/ReactiveCocoa,victorlin/ReactiveCocoa,mattpetters/ReactiveCocoa,LHDsimon/ReactiveCocoa,tipbit/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,OneSmallTree/ReactiveCocoa,wpstarnice/ReactiveCocoa,taylormoonxu/ReactiveCocoa,KuPai32G/ReactiveCocoa,ShawnLeee/ReactiveCocoa,libiao88/ReactiveCocoa,FelixYin66/ReactiveCocoa,JackLian/ReactiveCocoa,CQXfly/ReactiveCocoa,brasbug/ReactiveCocoa,j364960953/ReactiveCocoa,KuPai32G/ReactiveCocoa,KJin99/ReactiveCocoa,taylormoonxu/ReactiveCocoa,ericzhou2008/ReactiveCocoa,zhigang1992/ReactiveCocoa,SuPair/ReactiveCocoa,icepy/ReactiveCocoa,yytong/ReactiveCocoa,yaoxiaoyong/ReactiveCocoa,kiurentu/ReactiveCocoa,WEIBP/ReactiveCocoa,SmartEncounter/ReactiveCocoa,llb1119/test,Liquidsoul/ReactiveCocoa,zzqiltw/ReactiveCocoa,gabemdev/ReactiveCocoa,Remitly/ReactiveCocoa,andersio/ReactiveCocoa,sugar2010/ReactiveCocoa,cnbin/ReactiveCocoa,juliangrosshauser/ReactiveCocoa,msdgwzhy6/ReactiveCocoa,goodheart/ReactiveCocoa,terry408911/ReactiveCocoa,JohnJin007/ReactiveCocoa,BrooksWon/ReactiveCocoa,libiao88/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,chao95957/ReactiveCocoa,leelili/ReactiveCocoa,yonekawa/ReactiveCocoa,tipbit/ReactiveCocoa,ailyanlu/ReactiveCocoa,nikita-leonov/ReactiveCocoa,jsslai/ReactiveCocoa,alvinvarghese/ReactiveCocoa,hbucius/ReactiveCocoa,windgo/ReactiveCocoa,esttorhe/ReactiveCocoa,vincentiss/ReactiveCocoa,eliperkins/ReactiveCocoa,AndyZhaoHe/ReactiveCocoa,lixar/ReactiveCocoa,LHDsimon/ReactiveCocoa,xumaolin/ReactiveCocoa,qq644531343/ReactiveCocoa,CQXfly/ReactiveCocoa,335g/ReactiveCocoa,shaohung001/ReactiveCocoa,smilypeda/ReactiveCocoa,yoichitgy/ReactiveCocoa,jam891/ReactiveCocoa,sujeking/ReactiveCocoa,jaylib/ReactiveCocoa,mtxs007/ReactiveCocoa,brightcove/ReactiveCocoa,sandyway/ReactiveCocoa,bencochran/ReactiveCocoa,eyu1988/ReactiveCocoa,ztchena/ReactiveCocoa,bscarano/ReactiveCocoa,Pingco/ReactiveCocoa,AndyZhaoHe/ReactiveCocoa,SuPair/ReactiveCocoa,mxxiv/ReactiveCocoa,stupidfive/ReactiveCocoa,RuiAAPeres/ReactiveCocoa,tornade0913/ReactiveCocoa,brasbug/ReactiveCocoa,Adlai-Holler/ReactiveCocoa,yytong/ReactiveCocoa,FelixYin66/ReactiveCocoa,Ricowere/ReactiveCocoa,hilllinux/ReactiveCocoa,richeterre/ReactiveCocoa,Khan/ReactiveCocoa,clg0118/ReactiveCocoa,zhukaixy/ReactiveCocoa,jeelun/ReactiveCocoa,jaylib/ReactiveCocoa,SuPair/ReactiveCocoa,cstars135/ReactiveCocoa,AlanJN/ReactiveCocoa,Carthage/ReactiveCocoa,esttorhe/ReactiveCocoa,eliperkins/ReactiveCocoa,nickcheng/ReactiveCocoa,ceekayel/ReactiveCocoa,imkerberos/ReactiveCocoa,zhukaixy/ReactiveCocoa,buildo/ReactiveCocoa,nickcheng/ReactiveCocoa,DreamHill/ReactiveCocoa,ShawnLeee/ReactiveCocoa,OnTheWay1988/ReactiveCocoa,hilllinux/ReactiveCocoa,paulyoung/ReactiveCocoa,stevielu/ReactiveCocoa,kevin-zqw/ReactiveCocoa,terry408911/ReactiveCocoa,LHDsimon/ReactiveCocoa,bencochran/ReactiveCocoa,ericzhou2008/ReactiveCocoa,beni55/ReactiveCocoa,dullgrass/ReactiveCocoa,jackywpy/ReactiveCocoa,ddc391565320/ReactiveCocoa,bensonday/ReactiveCocoa,j364960953/ReactiveCocoa,kaylio/ReactiveCocoa,paulyoung/ReactiveCocoa,200895045/ReactiveCocoa,bensonday/ReactiveCocoa,xiaobing2007/ReactiveCocoa,zhaoguohui/ReactiveCocoa,goodheart/ReactiveCocoa,shaohung001/ReactiveCocoa,leelili/ReactiveCocoa,ioshger0125/ReactiveCocoa,Ethan89/ReactiveCocoa,gengjf/ReactiveCocoa,hj3938/ReactiveCocoa,isghe/ReactiveCocoa,tonyli508/ReactiveCocoa,kaylio/ReactiveCocoa,cstars135/ReactiveCocoa,xumaolin/ReactiveCocoa,howandhao/ReactiveCocoa,kiurentu/ReactiveCocoa,takeshineshiro/ReactiveCocoa,mtxs007/ReactiveCocoa,clg0118/ReactiveCocoa,chao95957/ReactiveCocoa,stupidfive/ReactiveCocoa,sugar2010/ReactiveCocoa,bensonday/ReactiveCocoa,yangshengchaoios/ReactiveCocoa,isghe/ReactiveCocoa,koamac/ReactiveCocoa,Ricowere/ReactiveCocoa,zhigang1992/ReactiveCocoa,calebd/ReactiveCocoa,xiaobing2007/ReactiveCocoa,andersio/ReactiveCocoa,zzqiltw/ReactiveCocoa,cogddo/ReactiveCocoa,yonekawa/ReactiveCocoa,KJin99/ReactiveCocoa,jaylib/ReactiveCocoa,xiaoliyang/ReactiveCocoa,Eveian/ReactiveCocoa,bencochran/ReactiveCocoa,kiurentu/ReactiveCocoa,DreamHill/ReactiveCocoa,ioshger0125/ReactiveCocoa,koamac/ReactiveCocoa,jsslai/ReactiveCocoa,liufeigit/ReactiveCocoa,bscarano/ReactiveCocoa,xulibao/ReactiveCocoa,jaylib/ReactiveCocoa,add715/ReactiveCocoa,luerhouhou/ReactiveCocoa,monkeydbobo/ReactiveCocoa,Farteen/ReactiveCocoa,eyu1988/ReactiveCocoa,hj3938/ReactiveCocoa,takeshineshiro/ReactiveCocoa,Rupert-RR/ReactiveCocoa,hilllinux/ReactiveCocoa,nikita-leonov/ReactiveCocoa,leelili/ReactiveCocoa,andersio/ReactiveCocoa,zxq3220122/ReactiveCocoa,jianwoo/ReactiveCocoa,buildo/ReactiveCocoa,jianwoo/ReactiveCocoa,natestedman/ReactiveCocoa,calebd/ReactiveCocoa,rpowelll/ReactiveCocoa,ailyanlu/ReactiveCocoa,alvinvarghese/ReactiveCocoa,bscarano/ReactiveCocoa,icepy/ReactiveCocoa,fanghao085/ReactiveCocoa,KuPai32G/ReactiveCocoa,yangyangluoluo/ReactiveCocoa,shuxiashusheng/ReactiveCocoa,Remitly/ReactiveCocoa,towik/ReactiveCocoa,tzongw/ReactiveCocoa,tiger8888/ReactiveCocoa,fhchina/ReactiveCocoa,lixar/ReactiveCocoa,gengjf/ReactiveCocoa,yytong/ReactiveCocoa,itschaitanya/ReactiveCocoa,emodeqidao/ReactiveCocoa,yangshengchaoios/ReactiveCocoa,add715/ReactiveCocoa,victorlin/ReactiveCocoa,SanChain/ReactiveCocoa,ddc391565320/ReactiveCocoa,JackLian/ReactiveCocoa,mxxiv/ReactiveCocoa,loupman/ReactiveCocoa,GuitarPlayer-Ma/ReactiveCocoa,almassapargali/ReactiveCocoa,335g/ReactiveCocoa,tonyli508/ReactiveCocoa,jam891/ReactiveCocoa,liufeigit/ReactiveCocoa,JohnJin007/ReactiveCocoa,pzw224/ReactiveCocoa,xulibao/ReactiveCocoa,walkingsmarts/ReactiveCocoa,sujeking/ReactiveCocoa,WEIBP/ReactiveCocoa,DongDongDongDong/ReactiveCocoa,emodeqidao/ReactiveCocoa,wangqi211/ReactiveCocoa,Adlai-Holler/ReactiveCocoa,sandyway/ReactiveCocoa,natan/ReactiveCocoa,koamac/ReactiveCocoa,AlanJN/ReactiveCocoa,longv2go/ReactiveCocoa,zxq3220122/ReactiveCocoa,Pingco/ReactiveCocoa,almassapargali/ReactiveCocoa,jsslai/ReactiveCocoa,kevin-zqw/ReactiveCocoa,Khan/ReactiveCocoa,monkeydbobo/ReactiveCocoa,OneSmallTree/ReactiveCocoa,Eveian/ReactiveCocoa,richeterre/ReactiveCocoa,stupidfive/ReactiveCocoa,itschaitanya/ReactiveCocoa,PSPDFKit-labs/ReactiveCocoa,tzongw/ReactiveCocoa,hoanganh6491/ReactiveCocoa,Farteen/ReactiveCocoa,zhenlove/ReactiveCocoa,loupman/ReactiveCocoa,KJin99/ReactiveCocoa,yizzuide/ReactiveCocoa,AndyZhaoHe/ReactiveCocoa,cnbin/ReactiveCocoa,fanghao085/ReactiveCocoa,walkingsmarts/ReactiveCocoa,Khan/ReactiveCocoa,towik/ReactiveCocoa,imkerberos/ReactiveCocoa,BlessNeo/ReactiveCocoa,windgo/ReactiveCocoa,dskatz22/ReactiveCocoa,zhaoguohui/ReactiveCocoa,cogddo/ReactiveCocoa,dachaoisme/ReactiveCocoa,Carthage/ReactiveCocoa,SmartEncounter/ReactiveCocoa,SanChain/ReactiveCocoa,buildo/ReactiveCocoa,pzw224/ReactiveCocoa,Ricowere/ReactiveCocoa,goodheart/ReactiveCocoa,200895045/ReactiveCocoa,yizzuide/ReactiveCocoa,libiao88/ReactiveCocoa,ohwutup/ReactiveCocoa,msdgwzhy6/ReactiveCocoa,hj3938/ReactiveCocoa,cogddo/ReactiveCocoa,Ricowere/ReactiveCocoa,brightcove/ReactiveCocoa,smilypeda/ReactiveCocoa,smilypeda/ReactiveCocoa,WEIBP/ReactiveCocoa,tzongw/ReactiveCocoa,vincentiss/ReactiveCocoa,on99/ReactiveCocoa,wangqi211/ReactiveCocoa,calebd/ReactiveCocoa,itschaitanya/ReactiveCocoa,SanChain/ReactiveCocoa,ohwutup/ReactiveCocoa,sujeking/ReactiveCocoa,ioshger0125/ReactiveCocoa,tornade0913/ReactiveCocoa,sdhzwm/ReactiveCocoa,GuitarPlayer-Ma/ReactiveCocoa,BlessNeo/ReactiveCocoa,brightcove/ReactiveCocoa,valleyman86/ReactiveCocoa,natestedman/ReactiveCocoa,jrmiddle/ReactiveCocoa,dz1111/ReactiveCocoa,msdgwzhy6/ReactiveCocoa,chieryw/ReactiveCocoa,nikita-leonov/ReactiveCocoa,natan/ReactiveCocoa,RuiAAPeres/ReactiveCocoa,PSPDFKit-labs/ReactiveCocoa,Rupert-RR/ReactiveCocoa,llb1119/test,huiping192/ReactiveCocoa,shuxiashusheng/ReactiveCocoa,BrooksWon/ReactiveCocoa,dskatz22/ReactiveCocoa,ceekayel/ReactiveCocoa,takeshineshiro/ReactiveCocoa,hoanganh6491/ReactiveCocoa,zxq3220122/ReactiveCocoa,gengjf/ReactiveCocoa,rpowelll/ReactiveCocoa,Juraldinio/ReactiveCocoa,OnTheWay1988/ReactiveCocoa,sdhzwm/ReactiveCocoa,fanghao085/ReactiveCocoa,CCOOOOLL/ReactiveCocoa,hbucius/ReactiveCocoa,PSPDFKit-labs/ReactiveCocoa,sdhzwm/ReactiveCocoa,jeelun/ReactiveCocoa,kevin-zqw/ReactiveCocoa,yaoxiaoyong/ReactiveCocoa,alvinvarghese/ReactiveCocoa,richeterre/ReactiveCocoa,Farteen/ReactiveCocoa,jrmiddle/ReactiveCocoa,monkeydbobo/ReactiveCocoa,cnbin/ReactiveCocoa,xiaoliyang/ReactiveCocoa,Adlai-Holler/ReactiveCocoa,towik/ReactiveCocoa,lixar/ReactiveCocoa,on99/ReactiveCocoa,windgo/ReactiveCocoa,Ray0218/ReactiveCocoa,yangyangluoluo/ReactiveCocoa,isghe/ReactiveCocoa,zhiwen1024/ReactiveCocoa,emodeqidao/ReactiveCocoa,brasbug/ReactiveCocoa,JackLian/ReactiveCocoa,dullgrass/ReactiveCocoa,Juraldinio/ReactiveCocoa,jeelun/ReactiveCocoa,tiger8888/ReactiveCocoa,huiping192/ReactiveCocoa,huiping192/ReactiveCocoa,swizzlr/ReactiveCocoa,tiger8888/ReactiveCocoa,juliangrosshauser/ReactiveCocoa,kaylio/ReactiveCocoa,qq644531343/ReactiveCocoa,DongDongDongDong/ReactiveCocoa,AlanJN/ReactiveCocoa,mattpetters/ReactiveCocoa,ailyanlu/ReactiveCocoa,zhiwen1024/ReactiveCocoa,gabemdev/ReactiveCocoa,yonekawa/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,esttorhe/ReactiveCocoa,ztchena/ReactiveCocoa,Ethan89/ReactiveCocoa,ceekayel/ReactiveCocoa,jianwoo/ReactiveCocoa,Pikdays/ReactiveCocoa,yizzuide/ReactiveCocoa,zzzworm/ReactiveCocoa,howandhao/ReactiveCocoa,zzzworm/ReactiveCocoa,qq644531343/ReactiveCocoa,stevielu/ReactiveCocoa,howandhao/ReactiveCocoa,almassapargali/ReactiveCocoa,luerhouhou/ReactiveCocoa,stevielu/ReactiveCocoa,victorlin/ReactiveCocoa,zhenlove/ReactiveCocoa,BlessNeo/ReactiveCocoa,rpowelll/ReactiveCocoa,swizzlr/ReactiveCocoa,chieryw/ReactiveCocoa,xulibao/ReactiveCocoa,xiaobing2007/ReactiveCocoa,sugar2010/ReactiveCocoa,CQXfly/ReactiveCocoa,xiaoliyang/ReactiveCocoa,mattpetters/ReactiveCocoa,Juraldinio/ReactiveCocoa,beni55/ReactiveCocoa,terry408911/ReactiveCocoa,natan/ReactiveCocoa,JohnJin007/ReactiveCocoa,longv2go/ReactiveCocoa,hoanganh6491/ReactiveCocoa,eyu1988/ReactiveCocoa,Carthage/ReactiveCocoa