ci docs: Add note that the .travis.yml assumes bundle install.
ci docs: Add note that the .travis.yml assumes bundle install.

Closes #3660

MauroMrod/jekyll,nickg33/jekyll,ZainRizvi/jekyll,goragod/jekyll,supriyantomaftuh/jekyll,drobati/jekyll,christophermanning/jekyll,alfredxing/jekyll,Tyrion22/jekyll,egobrightan/jekyll,bsmr-ruby/jekyll,chiyodad/jekyll,zsyed91/jekyll,howkj1/jekyll,ajhit406/jekyll,alfredxing/jekyll,jmknoll/jekyll,xantage/jekyll,htmelvis/jekyll,gaosboy/jekyll,18F/jekyll,rebornix/jekyll,AaronSikes/jekyll,anthonyrosengren/grasshoppergathering2.github-io,fengsmith/jekyllcn,angeliaz/jekyll,sanxore/sanxore.github.com,pheuko/jekyll,julienbourdeau/jekyll,chrisfinazzo/jekyll,desidude03/jekyll,brint/jekyll,jmhardison/jekyll,PepSalehi/jekyll,gynter/jekyll,aarvay/jekyll,trungvothanh/jekyll,abhilashhb/jekyll,nasht00/jekyll,princeofdarkness76/jekyll,chinayin/jekyll,goragod/jekyll,jekyll/jekyll,CPVPLachlan/CPVP-Blog,AnanthaRajuC/jekyll,backendeveloper/jekyll,CheekyFE/jekyll,richsoni/jekyll,gaosboy/jekyll,vcgato29/jekyll,rajrathore/jekyll,shliujing/jekyll,codeclimate-testing/jekyll,krishnakalyan3/jekyll,wentixiaogege/jekyll,x-way/jekyll,xantage/jekyll,pmarsceill/jekyll,hubsaysnuaa/jekyll,xcatliu/jekyllcn,noikiy/jekyll,MjAbuz/jekyll,oresmus/jekyll,CorainChicago/jekyll,SQS2/Test,nasht00/jekyll,ramoslin02/jekyll,rlugojr/jekyll,dansef/jekyll,Teino1978-Corp/Teino1978-Corp-jekyll,eloyesp/jekyll,jmptrader/jekyll,zsyed91/jekyll,iRoxx/jekyll,honger05/jekyllcn,bsmr-ruby/jekyll,Tiger66639/jekyll,tomjohnson1492/jekyll,fengsmith/jekyll,digideskio/jekyll,Strangehill/jekyll,codeclimate-testing/jekyll,vcgato29/jekyll,dezon/jekyll,zhangkuaiji/jekyllcn,ducktyper/jekyll,anthonyrosengren/grasshoppergathering2.github-io,rovrevik/jekyll,fabulousu/jekyll,dansef/jekyll,ls2uper/jekyll,pheuko/jekyll,18F/jekyll,doubleday/jekyll,jeffkole/jekyll,floydpraveen/jekyll,ZDroid/jekyll,tomasdiez/jekyll,pmarsceill/jekyll,m2candre/jekyll,x-way/jekyll,tomjohnson1492/jekyll,jaybe-jekyll/jekyll,marrujoalex/jekyll,floydpraveen/jekyll,jmknoll/jekyll,omeripek/jekyll,rajrathore/jekyll,mrb/jekyll,SQS2/Test,penchan1218/jekyllcn,ZainRizvi/jekyll,shuber2/jekyll,noikiy/jekyll,christophermanning/jekyll,ewinkler/jekyll,chiyodad/jekyll,omeripek/jekyll,gkunwar/gkunwar.github.io,nemotan/jekyll,tylermachen/jekyll,FlyingWHR/jekyll,Teino1978-Corp/Teino1978-Corp-jekyll,trungvothanh/jekyll,wentixiaogege/jekyll,Teino1978-Corp/jekyll,Strangehill/jekyll,mixxmac/jekyll,wentixiaogege/jekyll,rlugojr/jekyll,zsyed91/jekyll,iRoxx/jekyll,alex-kovac/jekyll,chrisfinazzo/jekyll,iRoxx/jekyll,jekyll/jekyll,fulldecent/jekyll,tylermachen/jekyll,jmknoll/jekyll,johnnycastilho/jekyll,thejameskyle/jekyll,CheekyFE/jekyll,alihalabyah/jekyll,alex-kovac/jekyll,jmhardison/jekyll,CPVPLachlan/CPVP-Blog,daniel-beck/jekyll,eninya/jekyll,xiaoshaozi52/jekyll,jmptrader/jekyll,floydpraveen/jekyll,bsmr-ruby/jekyll,saitodisse/jekyll,ryanshaw/jekyll,matuzo/jekyll,drobati/jekyll,fulldecent/jekyll,Teino1978-Corp/Teino1978-Corp-jekyll,teju111/jekyll,Teino1978-Corp/jekyll,yhironaka/yhironaka.github.io,xcatliu/jekyllcn,rasa2011/rasa2011.github.io,marrujoalex/jekyll,isathish/jekyll,eninya/jekyll,zsyed91/jekyll,tugberkugurlu/jekyll,chrisfinazzo/jekyll,tareq-s/jekyll,jaroot32/jekyll,backendeveloper/jekyll,Kinghack/kinghack.github.com,htmelvis/jekyll,ZainRizvi/jekyll,jeffkole/jekyll,xiongjungit/jekyll,CorainChicago/jekyll,jekyll/jekyll,dezon/jekyll,alex-kovac/jekyll,bsmr-ruby/jekyll,CPVPLachlan/CPVP-Blog,ryanshaw/jekyll,xcatliu/jekyllcn,sanxore/sanxore.github.com,yihangho/jekyll,Kinghack/kinghack.github.com,ryanshaw/jekyll,krahman/jekyll,krishnakalyan3/jekyll,ramoslin02/jekyll,nasht00/jekyll,supriyantomaftuh/jekyll,rovrevik/jekyll,jmptrader/jekyll,foocoder/jekyll,nickg33/jekyll,sasongkojati/jekyll,adilapapaya/jekyll,winndows/jekyll,AtekiRyu/jekyll,ewinkler/jekyll,mixxmac/jekyll,isathish/jekyll,nasht00/jekyll,hartmel/jekyll,PepSalehi/jekyll,stomar/jekyll,nickg33/jekyll,saitodisse/jekyll,kuangyeheng/jekyll,UniFreak/jekyllcn,EddieDow/jekyll,MauroMrod/jekyll,foocoder/jekyll,winndows/jekyll,krahman/jekyll,AtekiRyu/jekyll,indraj/jekyll,larryfox/jekyll,fabulousu/jekyll,PepSalehi/jekyll,krishnakalyan3/jekyll,jekyll/jekyll,vidbina/jekyll,kuangyeheng/jekyll,likong/jekyll,zhangkuaiji/jekyllcn,honger05/jekyllcn,kimeng/jekyll,thejameskyle/jekyll,honger05/jekyllcn,aarvay/jekyll,thetaxman/jekyll,QuinntyneBrown/jekyll,codeclimate-testing/jekyll,CheekyFE/jekyll,gkunwar/gkunwar.github.io,ajhit406/jekyll,richsoni/jekyll,18F/jekyll,mrb/jekyll,AnanthaRajuC/jekyll,brint/jekyll,FlyingWHR/jekyll,doubleday/jekyll,likong/jekyll,ReachingOut/jekyll,tamouse/jekyll,getandpost/jekyll.github.io,jeffkole/jekyll,thetaxman/jekyll,penchan1218/jekyllcn,abhilashhb/jekyll,leichunxin/jekyll,chrisfinazzo/jekyll,richsoni/jekyll,ReachingOut/jekyll,royalwang/jekyll,martynbm/jekyll,leichunxin/jekyll,UniFreak/jekyllcn,adilapapaya/jekyll,hartmel/jekyll,sanxore/sanxore.github.com,Tyrion22/jekyll,UniFreak/jekyllcn,sasongkojati/jekyll,QuinntyneBrown/jekyll,oresmus/jekyll,Wirachmat/jekyll,jaybe-jekyll/jekyll,LuoPX-15510486969/jekyll,rebornix/jekyll,daniel-beck/jekyll,fulldecent/jekyll,julienbourdea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