fix #108, scope bundler bin to build
fix #108, scope bundler bin to build

guidance-guarantee-programme/heroku-buildpack-princexml-old,d-reinhold/cf-buildpack-ruby,rhomobile/heroku-buildpack-ruby,sky-uk/ruby-buildpack,Altoros/ruby-buildpack,zidekmat/buildpack-ruby,Altoros/ruby-buildpack,swipesense/heroku-buildpack-ruby,DigitalInnovation/heroku-buildpack-mslabs,thewebguy/heroku-buildpack-ruby-ffmpeg-libsndfile,takii/heroku-buildpack-ruby,travis-ci/heroku-buildpack-ruby,qstream/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,hpcloud/ruby-buildpack,sstelfox/buildpack-ruby,crdschurch/heroku-buildpack-ruby,Dim25/heroku-buildpack-ruby-GSL,Jonty/ruby-buildpack,wolfoo2931/heroku-buildpack-ruby-2a352ae,musicglue/heroku-buildpack-ruby,sanemat/heroku-buildpack-ruby-tachikoma,amaltson/heroku-buildpack-ruby,jonseaberg/heroku-buildpack-turbo-sprockets,codykrieger/heroku-buildpack-jekyll,bskyb-commerce/ruby-buildpack,rvizza/heroku-buildpack-gsl-ruby,packetmonkey/heroku-buildpack-ruby,jgable/buildpack-ruby-rack-setup-tasks,ltrademark/heroku-buildpack-ruby,Altoros/ruby-buildpack,moneyadviceservice/heroku-buildpack-ruby-bowndler,jumptvs/BP_Ruby,hatofmonkeys/ruby-testing-buildpack,CPPWind/ruby-buildpack,reesio/heroku-buildpack-ruby,redhotvengeance/heroku-buildpack-deep-thought,hpcloud/ruby-buildpack,aarongray/heroku-buildpack-ruby,orenyk/heroku-buildpack-ruby,jayshreeanand/heroku-buildpack-ruby,cloudn/buildpack-ruby,instacart/heroku-buildpack-ruby,fcruxen/ruby-buildpack,ndbroadbent/heroku-buildpack-turbo-sprockets,trumaker/heroku-buildpack-turbo-sprockets,Scalingo/ruby-buildpack,scottatron/moc-buildpack,space150/heroku-buildpack-ruby,tpope/heroku-buildpack-ruby-tpope,samfrench/heroku-buildpack-ruby,daltonrenaldo/heroku-buildpack-ruby,cordata/heroku-buildpack-ruby,dlorson/gentle-buildpack,tdenovan/heroku-buildpack-ruby,Altoros/ruby-buildpack,ekaranto/rails4-bluemix-buildpack,ilpoldo/heroku-buildpack-ruby,Git-Host/prelang-buildpack,tenjikinc/heroku-buildpack-ruby,lyoshenka/heroku-buildpack-ruby-jekyll,engineyard/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,bskyb-commerce/help-heroku-buildpack,orlando/heroku-buildpack-ruby,beydogan/ruby-buildpack,righi/instacart-heroku-buildpack,beydogan/ruby-buildpack,barakav/heroku-buildpack-ruby,ericboehs/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,ActiveState/heroku-buildpack-ruby,ericboehs/heroku-buildpack-ruby,brightbytes/heroku-buildpack-ruby-without-assets-precompile,vhx/heroku-buildpack,pkgr/heroku-buildpack-ruby,jumptvs/BP_Ruby,awebneck/heroku-buildpack-canvas,lyoshenka/heroku-buildpack-ruby-jekyll,sky-uk/ruby-buildpack,Nedomas/heroku-buildpack-ruby-minus-node-with-node-paths,barakav/heroku-buildpack-ruby,guidance-guarantee-programme/heroku-buildpack-princexml-old,ActiveState/heroku-buildpack-ruby,michaelphines/alexa-nest,iamjarvo/ruby-buildpack,mattmanning/heroku-buildpack-ruby-jekyll,phusion/heroku-buildpack-ruby,dtao/deft-buildpack-ruby,wakermahmud/heroku-buildpack-jekyll,moneyadviceservice/heroku-buildpack-ruby-bowndler,jeremyvdw/heroku-buildpack-ruby-jekyll,ibmdb/db2rubybuildpack,hixi/heroku-buildpack-ruby,fgbreel/heroku-buildpack-ruby,KoanHealth/heroku-buildpack-marvin-setup,ChefSteps/heroku-buildpack-ruby,Dim25/heroku-buildpack-ruby-GSL,mattwalters/heroku-buildpack-ruby,shuber/heroku-buildpack-ruby,mintybit/heroku-buildpack-ruby,bskyb-commerce/ruby-buildpack,wakermahmud/heroku-buildpack-jekyll,sky-uk/help-heroku-buildpack,rowanoulton/heroku-buildpack-ruby,0x00evil/heroku-buildpack-ruby,recursecenter/heroku-buildpack-ruby,DouglasAllen/heroku-buildpack-ruby,pkgr/buildpack-ruby-precise-old,packetmonkey/heroku-buildpack-ruby,takii/db2rubybuildpack,zoomer/heroku-buildpack-ruby-bower,ndbroadbent/heroku-buildpack-turbo-sprockets,phusion/heroku-buildpack-ruby,bwaite-jaroop/heroku-buildpack-ruby,jeremyvdw/heroku-buildpack-ruby-jekyll,cordata/heroku-buildpack-ruby,jgable/buildpack-ruby-rack-setup-tasks,diasks2/heroku-buildpack-mecab,DigitalInnovation/heroku-buildpack-mslabs,stefansundin/heroku-buildpack-ruby,mattwalters/heroku-buildpack-ruby,mrhenry/heroku-buildpack-ruby,bskyb-commerce/help-heroku-buildpack,cloudfoundry/ruby-buildpack,engineyard/heroku-buildpack-ruby,jumptvs/BP_Ruby,reesio/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,michaelphines/alexa-nest,vhx/heroku-buildpack,ericroberts/heroku-buildpack-ruby,Jonty/ruby-buildpack,dleavitt/heroku-buildpack-ruby,mperejda/heroku-buildpack-ruby,schu/buildpack-testing,brightbytes/heroku-buildpack-ruby-without-assets-precompile,DouglasAllen/heroku-buildpack-ruby,CPPWind/ruby-buildpack,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,pkgr/heroku-buildpack-ruby,pkgr/buildpack-ruby-precise-old,cloudn/buildpack-ruby,cloudn/buildpack-ruby,ascot21/heroku-buildpack-turbo-sprockets,dieze/heroku-buildpack-ruby-hooks,iamjarvo/ruby-buildpack,swipesense/heroku-buildpack-ruby,ibmdb/db2rubybuildpack,gls1/heroku-buildpack-ruby-pdftk-new,fgbreel/heroku-buildpack-ruby,fcruxen/ruby-buildpack,iamjarvo/ruby-buildpack,qstream/heroku-buildpack-ruby,Micka33/heroku-buildpack-ruby-liblua,DyegoCosta/heroku-buildpack-ruby,rhomobile/heroku-buildpack-ruby,electricobjects/heroku-buildpack-ruby,samfrench/heroku-buildpack-ruby,dtao/teeny-buildpack,sky-uk/ruby-buildpack,orlando/heroku-buildpack-ruby,jayshreeanand/heroku-buildpack-ruby,pkgr/buildpack-ruby-precise-old,allomov/fat-free-heroku-buildpack-ruby,rvizza/heroku-buildpack-gsl-ruby,jumptvs/BP_Ruby,leonardykris/mos-ruby-buildpack,phusion/heroku-buildpack-ruby,0x00evil/heroku-buildpack-ruby,erintherad/heroku-buildpack-ruby,Micka33/heroku-buildpack-ruby-liblua,ascot21/heroku-buildpack-turbo-sprockets,Jonty/ruby-buildpack,teodor-pripoae/heroku-buildpack-ruby,zoomer/heroku-buildpack-ruby-bower,d-reinhold/cf-buildpack-ruby,sky-uk/help-heroku-buildpack,HYPERHYPER/heroku-buildpack-ruby,cloudn/buildpack-ruby,erintherad/heroku-buildpack-ruby,andycroll/heroku-buildpack-jekyll,daltonrenaldo/heroku-buildpack-ruby,iamjarvo/ruby-buildpack,zunda/heroku-buildpack-ruby,mattmanning/heroku-buildpack-ruby-jekyll,hpcloud/heroku-buildpack-ruby,ablease/custom-buildpack,ltrademark/heroku-buildpack-ruby,mperejda/heroku-buildpack-ruby,tenjikinc/heroku-buildpack-ruby,mrhenry/heroku-buildpack-ruby,bskyb-commerce/ruby-buildpack,stolt45/heroku-buildpack-ruby-with-sqlite3,hatofmonkeys/ruby-testing-buildpack,takii/db2rubybuildpack,stolt45/heroku-buildpack-ruby-with-sqlite3,ericroberts/heroku-buildpack-ruby,dleavitt/heroku-buildpack-ruby,hixi/heroku-buildpack-ruby,takii/heroku-buildpack-ruby,gbenedict/heroku-buildpack-ruby,wolfoo2931/heroku-buildpack-ruby-2a352ae,simonnordberg/heroku-buildpack-ruby,sstelfox/buildpack-ruby,codykrieger/heroku-buildpack-jekyll,hellojustin/heroku-buildpack-custom-ruby,sanemat/heroku-buildpack-ruby-tachikoma,Scalingo/ruby-buildpack,anay/buildpack-ruby-with-oracle-jdk,icelab/heroku-buildpack-ruby,makifund/heroku-buildpack-ruby,travis-ci/heroku-buildpack-ruby,dtao/teeny-buildpack,pilotcreative/heroku-buildpack-ruby,tdenovan/heroku-buildpack-ruby,dtao/deft-buildpack-ruby,schu/buildpack-testing,d-reinhold/cf-buildpack-ruby,ilpoldo/heroku-buildpack-ruby,cloudControl/buildpack-ruby,dieze/heroku-buildpack-ruby-hooks,ekaranto/rails4-bluemix-buildpack,gls1/heroku-buildpack-ruby-pdftk,donnykurnia/heroku-buildpack-ruby,fcruxen/ruby-buildpack,hpcloud/heroku-buildpack-ruby,Genius/heroku-buildpack-ruby,ablease/custom-buildpack,jasonlevens/heroku-buildpack-ruby,KoanHealth/heroku-buildpack-marvin-setup,jasonlevens/heroku-buildpack-ruby,Git-Host/prelang-buildpack,diasks2/heroku-buildpack-mecab,tpope/heroku-buildpack-ruby-tpope,cloudControl/buildpack-ruby,schu/heroku-buildpack-ruby,qnyp/heroku-buildpack-ruby-bower,musicglue/heroku-buildpack-ruby,amaltson/heroku-buildpack-ruby,awebneck/heroku-buildpack-canvas,allomov/fat-free-heroku-buildpack-ruby,takii/db2rubybuildpack,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,Nedomas/heroku-buildpack-ruby-minus-node-with-node-paths,cloudfoundry/ruby-buildpack,pilotcreative/heroku-buildpack-ruby,crdschurch/heroku-buildpack-ruby,schu/heroku-buildpack-ruby,andycroll/heroku-buildpack-jekyll,recursecenter/heroku-buildpack-ruby,electricobjects/heroku-buildpack-ruby,tomwolfe/heroku-buildpack-gsl-ruby,trumaker/heroku-buildpack-turbo-sprockets,ruby/heroku-buildpack-www-ruby-lang,ibmdb/db2rubybuildpack,tomwolfe/heroku-buildpack-gsl-ruby,heroku/heroku-buildpack-ruby,HYPERHYPER/heroku-buildpack-ruby,qnyp/heroku-buildpack-ruby-bower,stefansundin/heroku-buildpack-ruby,donnykurnia/heroku-buildpack-ruby,jonseaberg/heroku-buildpack-turbo-sprockets,makifund/heroku-buildpack-ruby,jonasoberschweiber/heroku-buildpack-ruby,jonasoberschweiber/heroku-buildpack-ruby,bellycard/heroku-buildpack-ruby,heroku/heroku-buildpack-ruby,instacart/heroku-buildpack-ruby,travis-ci/heroku-buildpack-ruby,mintybit/heroku-buildpack-ruby,bskyb-commerce/ruby-buildpack,shuber/heroku-buildpack-ruby,rowanoulton/heroku-buildpack-ruby,gls1/heroku-buildpack-ruby-pdftk,icelab/heroku-buildpack-ruby,sky-uk/ruby-buildpack,CPPWind/ruby-buildpack,ablease/custom-buildpack,DyegoCosta/heroku-buildpack-ruby,Genius/heroku-buildpack-ruby,simonnordberg/heroku-buildpack-ruby,redhotvengeance/heroku-buildpack-deep-thought,ablease/custom-buildpack,hatofmonkeys/ruby-testing-buildpack,gbenedict/heroku-buildpack-ruby,aarongray/heroku-buildpack-ruby,CPPWind/ruby-buildpack,derrek/heroku-buildpack-ruby,sanemat/heroku-buildpack-ruby-tachikoma,fcruxen/ruby-buildpack,catalyzeio/buildpack-ruby,anay/buildpack-ruby-with-oracle-jdk,bwaite-jaroop/heroku-buildpack-ruby,orenyk/heroku-buildpack-ruby,takii/db2rubybuildpack,cmaggard/heroku-buildpack-turbo-sprockets,blueapron/heroku-buildpack-ruby,scottatron/moc-buildpack,space150/heroku-buildpack-ruby,Jonty/ruby-buildpack,zunda/heroku-buildpack-ruby,derrek/heroku-buildpack-ruby,cmaggard/heroku-buildpack-turbo-sprockets,hpcloud/ruby-buildpack,pietrop/heroku-buildpack-ruby,leonardykris/mos-ruby-buildpack,hellojustin/heroku-buildpack-custom-ruby,blueapron/heroku-buildpack-ruby,dlorson/gentle-buildpack,catalyzeio/buildpack-ruby,ChefSteps/heroku-buildpack-ruby,thewebguy/heroku-buildpack-ruby-ffmpeg-libsndfile,bellycard/heroku-buildpack-ruby,righi/instacart-heroku-buildpack,pietrop/heroku-buildpack-ruby,gls1/heroku-buildpack-ruby-pdftk-new,hpcloud/ruby-buildpack,teodor-pripoae/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,zidekmat/buildpack-ruby