Save scheduleDate, not the real date of execution
Save scheduleDate, not the real date of execution

The real date of execution may be deferred for any number of reasons,
and `throttle()` only cares that it _schedules_ values with the given
interval between them.

Also, only update `previousDate` if we’re actually going to send a
value.

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