Add rm -rf vendor/cache/ to troubleshooting steps
Add rm -rf vendor/cache/ to troubleshooting steps

Closes #723

pivotal-cf-experimental/bundler,wenderjean/bundler,tgxworld/bundler,pjump/bundler,gregkare/bundler,gentoo/bundler,TimMoore/bundler,roseweixel/bundler,wenderjean/bundler,zhangkuaiji/bundler,jingweno/bundler,carpodaster/bundler,sideci-sample/sideci-sample-bundler,jingweno/bundler,carpodaster/bundler,CorainChicago/bundler,Wirachmat/bundler,smlance/bundler,bundler/bundler,EasonYi/bundler,jaym/bundler,Teino1978-Corp/Teino1978-Corp-bundler,schaary/bundler,Eric-Guo/bundler,lgierth/bundler,smlance/bundler,mdorrance/bundler,seanlinsley/bundler,Eric-Guo/bundler,robinboening/bundler,haonaturel/bundler,pivotal-cf-experimental/bundler,frsyuki/bundler,mattbrictson/bundler-1,masarakki/bundler,RochesterinNYC/bundler,haonature/bundler,EasonYi/bundler,ngpestelos/bundler,seanlinsley/bundler,elovelan/bundler,haonature888/bundler,cdwort/bundler,RochesterinNYC/bundler,danimashu/bundler,raphael/bundler,mvz/bundler,danimashu/bundler,mvz/bundler,PG-kura/bundler,elovelan/bundler,anil826/bundler,pjump/bundler,neslom/bundler,eagletmt/bundler,h4ck3rm1k3/bundler,zhangkuaiji/bundler,mattbrictson/bundler-1,ximus/bundler,h4ck3rm1k3/bundler,EthanK28/bundler,kohgpat/bundler,steved/bundler,1337807/bundler,dilumnavanjana/bundler,mpapis/bundler,suhastech/bundler,jaym/bundler,masarakki/bundler,frsyuki/bundler,ngpestelos/bundler,AiyionPrime/bundler,asutoshpalai/bundler,CorainChicago/bundler,agis-/bundler,twcctz500000/bundler,mpapis/bundler,schaary/bundler,simplybusiness/bundler,gregkare/bundler,AiyionPrime/bundler,patvice/bundler,roseweixel/bundler,mdorrance/bundler,ximus/bundler,chulkilee/bundler,byroot/bundler,Elffers/bundler,simplybusiness/bundler,Wirachmat/bundler,Elffers/bundler,jasonkarns/bundler,kohgpat/bundler,ipmobiletech/bundler,mtscout6/bundler,philnash/bundler,agis-/bundler,anil826/bundler,JuanitoFatas/bundler,ligi/bundler,cowboyd/bundler,asutoshpalai/bundler,robinboening/bundler,rkh/bundler,patvice/bundler,suhastech/bundler,lmtim/bundler,asymmetric/bundler,bronzdoc/bundler,nju520/bundler,PG-kura/bundler,jasonkarns/bundler,steved/bundler,chulkilee/bundler,dilumnavanjana/bundler,nju520/bundler,christer155/bundler,asymmetric/bundler,cstrahan/bundler,philnash/bundler,haocafes/bundler,lmtim/bundler,Teino1978-Corp/Teino1978-Corp-bundler,EthanK28/bundler,davydovanton/bundler,davydovanton/bundler,vemmaverve/bundler,bronzdoc/bundler,chef/bundler,cstrahan/bundler,e2/bundler,cdwort/bundler,tgxworld/bundler,sideci-sample/sideci-sample-bundler,r7kamura/bundler,bundler/bundler,ducthanh/bundler,chef/bundler,TimMoore/bundler,ipmobiletech/bundler,byroot/bundler,christer155/bundler,joshsoftware/bundler,joshsoftware/bundler,ligi/bundler,neslom/bundler