add stack change spec tests
add stack change spec tests

ibmdb/db2rubybuildpack,DouglasAllen/heroku-buildpack-ruby,hpcloud/ruby-buildpack,tpope/heroku-buildpack-ruby-tpope,orlando/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,brightbytes/heroku-buildpack-ruby-without-assets-precompile,ekaranto/rails4-bluemix-buildpack,andycroll/heroku-buildpack-jekyll,hellojustin/heroku-buildpack-custom-ruby,erintherad/heroku-buildpack-ruby,sky-uk/help-heroku-buildpack,ndbroadbent/heroku-buildpack-turbo-sprockets,Jonty/ruby-buildpack,takii/db2rubybuildpack,pietrop/heroku-buildpack-ruby,barakav/heroku-buildpack-ruby,daltonrenaldo/heroku-buildpack-ruby,pietrop/heroku-buildpack-ruby,cloudn/buildpack-ruby,0x00evil/heroku-buildpack-ruby,pkgr/heroku-buildpack-ruby,space150/heroku-buildpack-ruby,jumptvs/BP_Ruby,hatofmonkeys/ruby-testing-buildpack,pilotcreative/heroku-buildpack-ruby,sky-uk/help-heroku-buildpack,dleavitt/heroku-buildpack-ruby,bwaite-jaroop/heroku-buildpack-ruby,DyegoCosta/heroku-buildpack-ruby,jumptvs/BP_Ruby,jayshreeanand/heroku-buildpack-ruby,fcruxen/ruby-buildpack,pkgr/heroku-buildpack-ruby,daltonrenaldo/heroku-buildpack-ruby,heroku/heroku-buildpack-ruby,CPPWind/ruby-buildpack,awebneck/heroku-buildpack-canvas,zoomer/heroku-buildpack-ruby-bower,icelab/heroku-buildpack-ruby,cmaggard/heroku-buildpack-turbo-sprockets,derrek/heroku-buildpack-ruby,moneyadviceservice/heroku-buildpack-ruby-bowndler,schu/heroku-buildpack-ruby,bwaite-jaroop/heroku-buildpack-ruby,zidekmat/buildpack-ruby,mintybit/heroku-buildpack-ruby,Micka33/heroku-buildpack-ruby-liblua,zidekmat/buildpack-ruby,jonasoberschweiber/heroku-buildpack-ruby,righi/instacart-heroku-buildpack,samfrench/heroku-buildpack-ruby,CPPWind/ruby-buildpack,mattmanning/heroku-buildpack-ruby-jekyll,beydogan/ruby-buildpack,takii/db2rubybuildpack,Jonty/ruby-buildpack,fgbreel/heroku-buildpack-ruby,Altoros/ruby-buildpack,bskyb-commerce/ruby-buildpack,leonardykris/mos-ruby-buildpack,ndbroadbent/heroku-buildpack-turbo-sprockets,bskyb-commerce/ruby-buildpack,dlorson/gentle-buildpack,diasks2/heroku-buildpack-mecab,hixi/heroku-buildpack-ruby,fgbreel/heroku-buildpack-ruby,cordata/heroku-buildpack-ruby,hpcloud/ruby-buildpack,ilpoldo/heroku-buildpack-ruby,space150/heroku-buildpack-ruby,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,electricobjects/heroku-buildpack-ruby,hpcloud/ruby-buildpack,gbenedict/heroku-buildpack-ruby,guidance-guarantee-programme/heroku-buildpack-princexml-old,jgable/buildpack-ruby-rack-setup-tasks,moneyadviceservice/heroku-buildpack-ruby-bowndler,Altoros/ruby-buildpack,amaltson/heroku-buildpack-ruby,ltrademark/heroku-buildpack-ruby,CPPWind/ruby-buildpack,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,cloudn/buildpack-ruby,Altoros/ruby-buildpack,jasonlevens/heroku-buildpack-ruby,gbenedict/heroku-buildpack-ruby,vhx/heroku-buildpack,brightbytes/heroku-buildpack-ruby-without-assets-precompile,recursecenter/heroku-buildpack-ruby,ablease/custom-buildpack,ablease/custom-buildpack,michaelphines/alexa-nest,codykrieger/heroku-buildpack-jekyll,samfrench/heroku-buildpack-ruby,iamjarvo/ruby-buildpack,cloudn/buildpack-ruby,jasonlevens/heroku-buildpack-ruby,jayshreeanand/heroku-buildpack-ruby,zunda/heroku-buildpack-ruby,packetmonkey/heroku-buildpack-ruby,vhx/heroku-buildpack,beydogan/ruby-buildpack,bellycard/heroku-buildpack-ruby,andycroll/heroku-buildpack-jekyll,lyoshenka/heroku-buildpack-ruby-jekyll,anay/buildpack-ruby-with-oracle-jdk,wakermahmud/heroku-buildpack-jekyll,ericroberts/heroku-buildpack-ruby,qnyp/heroku-buildpack-ruby-bower,pilotcreative/heroku-buildpack-ruby,righi/instacart-heroku-buildpack,instacart/heroku-buildpack-ruby,ruby/heroku-buildpack-www-ruby-lang,jonseaberg/heroku-buildpack-turbo-sprockets,guidance-guarantee-programme/heroku-buildpack-princexml-old,stefansundin/heroku-buildpack-ruby,schu/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,DouglasAllen/heroku-buildpack-ruby,Nedomas/heroku-buildpack-ruby-minus-node-with-node-paths,sky-uk/ruby-buildpack,ericboehs/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,ekaranto/rails4-bluemix-buildpack,fcruxen/ruby-buildpack,jonseaberg/heroku-buildpack-turbo-sprockets,rowanoulton/heroku-buildpack-ruby,sky-uk/ruby-buildpack,Jonty/ruby-buildpack,Altoros/ruby-buildpack,gls1/heroku-buildpack-ruby-pdftk-new,mintybit/heroku-buildpack-ruby,iamjarvo/ruby-buildpack,bskyb-commerce/help-heroku-buildpack,barakav/heroku-buildpack-ruby,mperejda/heroku-buildpack-ruby,takii/db2rubybuildpack,cordata/heroku-buildpack-ruby,orenyk/heroku-buildpack-ruby,iamjarvo/ruby-buildpack,mattmanning/heroku-buildpack-ruby-jekyll,swipesense/heroku-buildpack-ruby,icelab/heroku-buildpack-ruby,blueapron/heroku-buildpack-ruby,HYPERHYPER/heroku-buildpack-ruby,qstream/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,Scalingo/ruby-buildpack,ChefSteps/heroku-buildpack-ruby,swipesense/heroku-buildpack-ruby,Jonty/ruby-buildpack,fcruxen/ruby-buildpack,ltrademark/heroku-buildpack-ruby,engineyard/heroku-buildpack-ruby,stefansundin/heroku-buildpack-ruby,ablease/custom-buildpack,Dim25/heroku-buildpack-ruby-GSL,teodor-pripoae/heroku-buildpack-ruby,donnykurnia/heroku-buildpack-ruby,musicglue/heroku-buildpack-ruby,takii/heroku-buildpack-ruby,dleavitt/heroku-buildpack-ruby,blueapron/heroku-buildpack-ruby,Micka33/heroku-buildpack-ruby-liblua,anay/buildpack-ruby-with-oracle-jdk,simonnordberg/heroku-buildpack-ruby,DyegoCosta/heroku-buildpack-ruby,musicglue/heroku-buildpack-ruby,makifund/heroku-buildpack-ruby,dlorson/gentle-buildpack,schu/buildpack-testing,zunda/heroku-buildpack-ruby,cloudn/buildpack-ruby,ilpoldo/heroku-buildpack-ruby,shuber/heroku-buildpack-ruby,0x00evil/heroku-buildpack-ruby,orlando/heroku-buildpack-ruby,takii/heroku-buildpack-ruby,donnykurnia/heroku-buildpack-ruby,tenjikinc/heroku-buildpack-ruby,mperejda/heroku-buildpack-ruby,schu/buildpack-testing,ericroberts/heroku-buildpack-ruby,CPPWind/ruby-buildpack,dieze/heroku-buildpack-ruby-hooks,cloudfoundry/ruby-buildpack,simonnordberg/heroku-buildpack-ruby,tdenovan/heroku-buildpack-ruby,michaelphines/alexa-nest,wakermahmud/heroku-buildpack-jekyll,hellojustin/heroku-buildpack-custom-ruby,hatofmonkeys/ruby-testing-buildpack,packetmonkey/heroku-buildpack-ruby,Scalingo/ruby-buildpack,shuber/heroku-buildpack-ruby,ibmdb/db2rubybuildpack,electricobjects/heroku-buildpack-ruby,Genius/heroku-buildpack-ruby,ibmdb/db2rubybuildpack,gls1/heroku-buildpack-ruby-pdftk-new,iamjarvo/ruby-buildpack,bskyb-commerce/ruby-buildpack,catalyzeio/buildpack-ruby,Nedomas/heroku-buildpack-ruby-minus-node-with-node-paths,reesio/heroku-buildpack-ruby,codykrieger/heroku-buildpack-jekyll,heroku/heroku-buildpack-ruby,dieze/heroku-buildpack-ruby-hooks,ChefSteps/heroku-buildpack-ruby,bskyb-commerce/ruby-buildpack,erintherad/heroku-buildpack-ruby,reesio/heroku-buildpack-ruby,lyoshenka/heroku-buildpack-ruby-jekyll,amaltson/heroku-buildpack-ruby,recursecenter/heroku-buildpack-ruby,tdenovan/heroku-buildpack-ruby,ablease/custom-buildpack,zoomer/heroku-buildpack-ruby-bower,tenjikinc/heroku-buildpack-ruby,jumptvs/BP_Ruby,bellycard/heroku-buildpack-ruby,orenyk/heroku-buildpack-ruby,sky-uk/ruby-buildpack,derrek/heroku-buildpack-ruby,sky-uk/ruby-buildpack,teodor-pripoae/heroku-buildpack-ruby,fcruxen/ruby-buildpack,hatofmonkeys/ruby-testing-buildpack,leonardykris/mos-ruby-buildpack,tpope/heroku-buildpack-ruby-tpope,Dim25/heroku-buildpack-ruby-GSL,catalyzeio/buildpack-ruby,rowanoulton/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,hpcloud/ruby-buildpack,awebneck/heroku-buildpack-canvas,cloudControl/buildpack-ruby,qstream/heroku-buildpack-ruby,ericboehs/heroku-buildpack-ruby,aarongray/heroku-buildpack-ruby,Genius/heroku-buildpack-ruby,qnyp/heroku-buildpack-ruby-bower,HYPERHYPER/heroku-buildpack-ruby,hixi/heroku-buildpack-ruby,instacart/heroku-buildpack-ruby,cloudControl/buildpack-ruby,cmaggard/heroku-buildpack-turbo-sprockets,bskyb-commerce/help-heroku-buildpack,makifund/heroku-buildpack-ruby,diasks2/heroku-buildpack-mecab,jumptvs/BP_Ruby,engineyard/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,takii/db2rubybuildpack,aarongray/heroku-buildpack-ruby,jonasoberschweiber/heroku-buildpack-ruby,jgable/buildpack-ruby-rack-setup-tasks