Add travis' build status image to README
Add travis' build status image to README

pmdeazeta/doorkeeper,ezilocchi/doorkeeper,shivakumaarmgs/doorkeeper,kolorahl/doorkeeper,ministryofjustice/doorkeeper,6fusion/doorkeeper,phillbaker/doorkeeper,identification-io/doorkeeper,calfzhou/doorkeeper,stefania11/doorkeeper,kolorahl/doorkeeper,outstand/doorkeeper,doorkeeper-gem/doorkeeper,pmdeazeta/doorkeeper,nbulaj/doorkeeper,mavenlink/doorkeeper,vovimayhem/doorkeeper,CloudTags/doorkeeper,ukasiu/doorkeeper,ifeelgoods/doorkeeper,Tout/doorkeeper,AICIDNN/doorkeeper,ngpestelos/doorkeeper,EasterAndJay/doorkeeper,vovimayhem/doorkeeper,stefania11/doorkeeper,Tout/doorkeeper,telekomatrix/doorkeeper,outstand/doorkeeper,coinbase/modified-doorkeeper,ministryofjustice/doorkeeper,ezilocchi/doorkeeper,ifeelgoods/doorkeeper,mavenlink/doorkeeper,CloudTags/doorkeeper,ukasiu/doorkeeper,Uysim/doorkeeper,coinbase/modified-doorkeeper,outstand/doorkeeper,identification-io/doorkeeper,lalithr95/doorkeeper,jasl/doorkeeper,EasterAndJay/doorkeeper,GeekOnCoffee/doorkeeper,Uysim/doorkeeper,6fusion/doorkeeper,Tout/doorkeeper,AdStage/doorkeeper,jasl/doorkeeper,lalithr95/doorkeeper,jasl/doorkeeper,ValMilkevich/doorkeeper,nbulaj/doorkeeper,ifeelgoods/doorkeeper,dollarshaveclub/doorkeeper,telekomatrix/doorkeeper,AICIDNN/doorkeeper,mavenlink/doorkeeper,doorkeeper-gem/doorkeeper,daande/doorkeeper,moneytree/doorkeeper,doorkeeper-gem/doorkeeper,stormz/doorkeeper,shivakumaarmgs/doorkeeper,GeekOnCoffee/doorkeeper,CloudTags/doorkeeper,calfzhou/doorkeeper,ValMilkevich/doorkeeper,vanboom/doorkeeper,CloudTags/doorkeeper,stormz/doorkeeper,dk1234567/doorkeeper,moneytree/doorkeeper,AdStage/doorkeeper,daande/doorkeeper,coinbase/modified-doorkeeper,ngpestelos/doorkeeper,dollarshaveclub/doorkeeper,dk1234567/doorkeeper,vanboom/doorkeeper