Add docs for site.documents.
Add docs for site.documents.

Ref: #2295.

tomjohnson1492/jekyll,getandpost/jekyll.github.io,rlugojr/jekyll,chinayin/jekyll,thetaxman/jekyll,jeffkole/jekyll,tomasdiez/jekyll,egobrightan/jekyll,lcustodio/lcustodio.github.io_base,0x00evil/jekyll,AnanthaRajuC/jekyll,eninya/jekyll,ramoslin02/jekyll,akoeplinger/jekyll,AtekiRyu/jekyll,howkj1/jekyll,yhironaka/yhironaka.github.io,larryfox/jekyll,isathish/jekyll,alex-kovac/jekyll,kimeng/jekyll,indraj/jekyll,kuangyeheng/jekyll,chinayin/jekyll,stomar/jekyll,sideci-sample/sideci-sample-jekyll,vidbina/jekyll,tareq-s/jekyll,FlyingWHR/jekyll,tomjohnson1492/jekyll,ZainRizvi/jekyll,backendeveloper/jekyll,christophermanning/jekyll,desidude03/jekyll,doubleday/jekyll,CPVPLachlan/CPVP-Blog,adilapapaya/jekyll,nateberkopec/jekyll,Kinghack/kinghack.github.com,Tiger66639/jekyll,0x00evil/jekyll,tomasdiez/jekyll,x-way/jekyll,fulldecent/jekyll,1gitGrey/jekyll,tugberkugurlu/jekyll,doubleday/jekyll,AtekiRyu/jekyll,zsyed91/jekyll,backendeveloper/jekyll,superve/jekyll,wadaries/jekyll,christophermanning/jekyll,isathish/jekyll,xiongjungit/jekyll,tobscure/jekyll,tobscure/jekyll,pmarsceill/jekyll,fabulousu/jekyll,jekyll/jekyll,gynter/jekyll,thejameskyle/jekyll,rlugojr/jekyll,trungvothanh/jekyll,foocoder/jekyll,tugberkugurlu/jekyll,nemotan/jekyll,hiteshsuthar/jekyll,ewinkler/jekyll,getandpost/jekyll.github.io,oresmus/jekyll,CheekyFE/jekyll,honger05/jekyllcn,Teino1978-Corp/Teino1978-Corp-jekyll,alfredxing/jekyll,harrissoerja/jekyll,hubsaysnuaa/jekyll,indraj/jekyll,thejameskyle/jekyll,Strangehill/jekyll,supriyantomaftuh/jekyll,naughtyboy83/jekyll,winndows/jekyll,liukaijv/jekyll,gencer/jekyll,Tyrion22/jekyll,CorainChicago/jekyll,howkj1/jekyll,noikiy/jekyll,Strangehill/jekyll,xantage/jekyll,sasongkojati/jekyll,kinlane/jekyll,tylermachen/jekyll,LuoPX-15510486969/jekyll,xcatliu/jekyllcn,shliujing/jekyll,SQS2/Test,royalwang/jekyll,anthonyrosengren/grasshoppergathering2.github-io,matuzo/jekyll,MjAbuz/jekyll,martynbm/jekyll,ryanshaw/jekyll,0x00evil/jekyll,tillgrallert/jekyll,winndows/jekyll,dansef/jekyll,julienbourdeau/jekyll,gkunwar/gkunwar.github.io,gaosboy/jekyll,desidude03/jekyll,xtymichael/jekyll,alihalabyah/jekyll,jmepg/jekyll,larryfox/jekyll,ReachingOut/jekyll,fengsmith/jekyllcn,jmknoll/jekyll,cyberid41/jekyll,18F/jekyll,hartmel/jekyll,thetaxman/jekyll,royalwang/jekyll,xantage/jekyll,nasht00/jekyll,dangaute/eng,floydpraveen/jekyll,brint/jekyll,tugberkugurlu/jekyll,schaazzz/jekyll,pheuko/jekyll,krishnakalyan3/jekyll,xiongjungit/jekyll,Wirachmat/jekyll,gaosboy/jekyll,foocoder/jekyll,harrissoerja/jekyll,winndows/jekyll,pmarsceill/jekyll,abhilashhb/jekyll,princeofdarkness76/jekyll,mnuessler/jekyll,marrujoalex/jekyll,floydpraveen/jekyll,penchan1218/jekyllcn,ReachingOut/jekyll,darwin/jekyll,lazycai/lazycai.github.com,christophermanning/jekyll,zsyed91/jekyll,alex-kovac/jekyll,stevecrozz/jekyll,matuzo/jekyll,htmelvis/jekyll,jmhardison/jekyll,kimeng/jekyll,darwin/jekyll,fabulousu/jekyll,tylermachen/jekyll,codeclimate-testing/jekyll,x-way/jekyll,CorainChicago/jekyll,pheuko/jekyll,hartmel/jekyll,mixxmac/jekyll,vidbina/jekyll,omeripek/jekyll,jekyll/jekyll,LeuisKen/jekyllcn,ReachingOut/jekyll,wadaries/jekyll,ducktyper/jekyll,gkunwar/gkunwar.github.io,tamouse/jekyll,fabulousu/jekyll,Teino1978-Corp/jekyll,lcustodio/lcustodio.github.io_base,teju111/jekyll,nathanhorrigan1/webdeveloper,alex-kovac/jekyll,gencer/jekyll,shuber2/jekyll,stomar/jekyll,vcgato29/jekyll,derekgottlieb/jekyll,lazycai/lazycai.github.com,johnnycastilho/jekyll,1gitGrey/jekyll,ajhit406/jekyll,jmknoll/jekyll,sasongkojati/jekyll,fengsmith/jekyll,QuinntyneBrown/jekyll,jmknoll/jekyll,leichunxin/jekyll,egobrightan/jekyll,bsmr-ruby/jekyll,wentixiaogege/jekyll,QuinntyneBrown/jekyll,rajrathore/jekyll,jeffkole/jekyll,krahman/jekyll,aarvay/jekyll,oresmus/jekyll,CPVPLachlan/CPVP-Blog,pmarsceill/jekyll,sanxore/sanxore.github.com,floydpraveen/jekyll,AtekiRyu/jekyll,garvitr/jekyll,backendeveloper/jekyll,m2candre/jekyll,gynter/jekyll,Tyrion22/jekyll,wentixiaogege/jekyll,supriyantomaftuh/jekyll,vcgato29/jekyll,alihalabyah/jekyll,mixxmac/jekyll,iRoxx/jekyll,Teino1978-Corp/jekyll,tylermachen/jekyll,Strangehill/jekyll,tareq-s/jekyll,gencer/jekyll,LuoPX-15510486969/jekyll,18F/jekyll,tomjohnson1492/jekyll,ryanshaw/jekyll,zhangkuaiji/jekyllcn,hartmel/jekyll,iRoxx/jekyll,nathanhorrigan1/webdeveloper,chrisfinazzo/jekyll,iRoxx/jekyll,chrisfinazzo/jekyll,MauroMrod/jekyll,leichunxin/jekyll,wentixiaogege/jekyll,PepSalehi/jekyll,cyberid41/jekyll,dangaute/eng,dansef/jekyll,LeuisKen/jekyllcn,rasa2011/rasa2011.github.io,imaustink/jekyll,xiongjungit/jekyll,EddieDow/jekyll,chiyodad/jekyll,jaybe-jekyll/jekyll,UniFreak/jekyllcn,schaazzz/jekyll,alfredxing/jekyll,AnanthaRajuC/jekyll,garvitr/jekyll,noikiy/jekyll,LuoPX-15510486969/jekyll,drobati/jekyll,ducktyper/jekyll,likong/jekyll,abhilashhb/jekyll,oresmus/jekyll,mrb/jekyll,xiebinhqy/jklly_china,xcatliu/jekyllcn,julienbourdeau/jekyll,imaustink/jekyll,martynbm/jekyll,imaustink/jekyll,likong/jekyll,alihalabyah/jekyll,nemotan/jekyll,rebornix/jekyll,trungvothanh/jekyll,pheuko/jekyll,likong/jekyll,stomar/jekyll,daniel-beck/jekyll,angeliaz/jekyll,ajhit406/jekyll,sanxore/sanxore.github.com,mrb/jekyll,princeofdarkness76/jekyll,chiyodad/jekyll,fengsmith/jekyllcn,jmptrader/jekyll,leichunxin/jekyll,dezon/jekyll,18F/jekyll,royalwang/jekyll,dezon/jekyll,superve/jekyll,goodtouch/jekyll,omeripek/jekyll,jekyll/jekyll,Tiger66639/jekyll,eloyesp/jekyll,greent2008/jekyll,wadaries/jekyll,sideci-sample/sideci-sample-jekyll,akoeplinger/jekyll,rlugojr/jekyll,ls2uper/jekyll,vidbina/jekyll,CheekyFE/jekyll,htmelvis/jekyll,EddieDow/jekyll,alex-kovac/jekyll,desidude03/jekyll,nasht00/jekyll,jekyll/jekyll,gkunwar/gkunwar.github.io,mixxmac/jekyll,fulldecent/jekyll,rebornix/jekyll,gencer/jekyll,pmarsceill/jekyll,princeofdarkness76/jekyll,harrissoerja/jekyll,jeffkole/jekyll,Teino1978-Corp/jekyll,princeofdarkness76/jekyll,xiebinhqy/jklly_china,indraj/jekyll,ls2uper/jekyll,sasongkojati/jekyll,thejameskyle/jekyll,eloyesp/jekyll,lazycai/lazycai.github.com,digideskio/jekyll,rajrathore/jekyll,johnnycastilho/jekyll,Wirachmat/jekyll,monxim/monxim.github.io,supriyantomaftuh/jekyll,derekgottlieb/jekyll,darwin/jekyll,Teino1978-Corp/Teino1978-Corp-jekyll,Strangehill/jekyll,m2candre/jekyll,krahman/jekyll,ewinkler/jekyll,xiebinhqy/jklly_china,marrujoalex/jekyll,eninya/jekyll,garvitr/jekyll,tomjohnson1492/jekyll,jaybe-jekyll/jekyll,tillgrallert/jekyll,Tiger66639/jekyll,shliujing/jekyll,brint/jekyll,hiteshsuthar/jekyll,mrb/jekyll,m2candre/jekyll,honger05/jekyllcn,AaronSikes/jekyll,noikiy/jekyll,tomasdiez/jekyll,saitodisse/jekyll,greent2008/jekyll,dezon/jekyll,ZainRizvi/jekyll,richsoni/jekyll,floydpraveen/jekyll,ryanshaw/jekyll,daniel-beck/jekyll,noikiy/jekyll,saitodisse/jekyll,Strangehill/jekyll,tomjohnson1492/jekyll,penchan1218/jekyllcn,goragod/jekyll,zsyed91/jekyll,liukaijv/jekyll,SQS2/Test,htmelvis/jekyll,Kinghack/kinghack.github.com,derekgottlieb/jekyll,alex-kovac/jekyll,derekgottlieb/jekyll,krahman/jekyll,stevecrozz/jekyll,nickg33/jekyll,tareq-s/jekyll,marrujoalex/jekyll,naughtyboy83/jekyll,naughtyboy83/jekyll,xantage/jekyll,tillgrallert/jekyll,kuangyeheng/jekyll,ajhit406/jekyll,jaybe-jekyll/jekyll,kinlane/jekyll,chiyodad/jekyll,ewinkler/jekyll,ducktyper/jekyll,martynbm/jekyll,rasa2011/rasa2011.github.io,jmhardison/jekyll,yihangho/jekyll,krishnakalyan3/jekyll,codeclimate-testing/jekyll,nasht00/jekyll,jaybe-jekyll/jekyll,jmhardison/jekyll,dangaute/eng,jaroot32/jekyll,doubleday/jekyll,CorainChicago/jekyll,fulldecent/jekyll,xtymichael/jekyll,shuber2/jekyll,goragod/jekyll,anthonyrosengren/grasshoppergathering2.github-io,ajhit406/jekyll,aarvay/jekyll,AaronSikes/jekyll,jeffkole/jekyll,MjAbuz/jekyll,gynter/jekyll,Kinghack/kinghack.github.com,hubsaysnuaa/jekyll,ryanshaw/jekyll,hubsaysnuaa/jekyll,goragod/jekyll,fengsmith/jekyll,nateberkopec/jekyll,chinayin/jekyll,brint/jekyll,ZainRizvi/jekyll,superve/jekyll,mnuessler/jekyll,tillgrallert/jekyll,foocoder/jekyll,vcgato29/jekyll,rlugojr/jekyll,CheekyFE/jekyll,FlyingWHR/jekyll,UniFreak/jekyllcn,QuinntyneBrown/jekyll,xiaoshaozi52/jekyll,digideskio/jekyll,hiteshsuthar/jekyll,rovrevik/jekyll,nathanhorrigan1/webdeveloper,omeripek/jekyll,jmepg/jekyll,xcatliu/jekyllcn,saitodisse/jekyll,johnnycastilho/jekyll,ls2uper/jekyll,alfredxing/jekyll,angeliaz/jekyll,lcustodio/lcustodio.github.io_base,thetaxman/jekyll,abhilashhb/jekyll,ramoslin02/jekyll,adilapapaya/jekyll,Wirachmat/jekyll,CPVPLachlan/CPVP-Blog,PepSalehi/jekyll,jaroot32/jekyll,bsmr-ruby/jekyll,SQS2/Test,eninya/jekyll,nickg33/jekyll,EddieDow/jekyll,nasht00/jekyll,xiebinhqy/jklly_china,dansef/jekyll,yihangho/jekyll,egobrightan/jekyll,mrb/jekyll,tillgrallert/jekyll,MjAbuz/jekyll,FlyingWHR/jekyll,gaosboy/jekyll,AaronSikes/jekyll,bsmr-ruby/jekyll,ramoslin02/jekyll,fengsmith/jekyll,rajrathore/jekyll,schaazzz/jekyll,kuangyeheng/jekyll,rongl/jekyll,jmepg/jekyll,xtymichael/jekyll,daniel-beck/jekyll,zhangkuaiji/jekyllcn,monxim/monxim.github.io,honger05/jekyllcn,chrisfinazzo/jekyll,nateberkopec/jekyll,stevecrozz/jekyll,liukaijv/jekyll,penchan1218/jekyllcn,LeuisKen/jekyllcn,larryfox/jekyll,zsyed91/jekyll,cyberid41/jekyll,tamouse/jekyll,kimeng/jekyll,x-way/jekyll,tamouse/jekyll,trungvothanh/jekyll,ZDroid/jekyll,teju111/jekyll,ZDroid/jekyll,PepSalehi/jekyll,Tyrion22/jekyll,rongl/jekyll,shuber2/jekyll,MauroMrod/jekyll,codeclimate-testing/jekyll,adilapapaya/jekyll,AnanthaRajuC/jekyll,richsoni/jekyll,x-way/jekyll,jaroot32/jekyll,jmptrader/jekyll,teju111/jekyll,goodtouch/jekyll,yihangho/jekyll,zhangkuaiji/jekyllcn,julienbourdeau/jekyll,anthonyrosengren/grasshoppergathering2.github-io,greent2008/jekyll,MauroMrod/jekyll,gencer/jekyll,xiaoshaozi52/jekyll,darwin/jekyll,drobati/jekyll,rovrevik/jekyll,xiaoshaozi52/jekyll,matuzo/jekyll,nickg33/jekyll,tobscure/jekyll,aarvay/jekyll,sanxore/sanxore.github.com,brint/jekyll,shliujing/jekyll,jmptrader/jekyll,ZDroid/jekyll,eloyesp/jekyll,xcatliu/jekyllcn,richsoni/jekyll,howkj1/jekyll,alfredxing/jekyll,rovrevik/jekyll,mnuessler/jekyll,rongl/jekyll,Teino1978-Corp/Teino1978-Corp-jekyll,fengsmith/jekyllcn,bsmr-ruby/jekyll,getandpost/jekyll.github.io,stomar/jekyll,rasa2011/rasa2011.github.io,UniFreak/jekyllcn,chrisfinazzo/jekyll,angeliaz/jekyll,rebornix/jekyll,drobati/jekyll,fulldecent/jekyll,nemotan/jekyll,lazycai/lazycai.github.com,isathish/jekyll,digideskio/jekyll,krishnakalyan3/jekyll