Fix previous slug download in Rake task
Fix previous slug download in Rake task

Genius/heroku-buildpack-ruby,qnyp/heroku-buildpack-ruby-bower,pilotcreative/heroku-buildpack-ruby,pilotcreative/heroku-buildpack-ruby,pkgr/heroku-buildpack-ruby,donnykurnia/heroku-buildpack-ruby,tpope/heroku-buildpack-ruby-tpope,orenyk/heroku-buildpack-ruby,ericboehs/heroku-buildpack-ruby,zunda/heroku-buildpack-ruby,brightbytes/heroku-buildpack-ruby-without-assets-precompile,makifund/heroku-buildpack-ruby,heroku/heroku-buildpack-ruby,makifund/heroku-buildpack-ruby,moneyadviceservice/heroku-buildpack-ruby-bowndler,tpope/heroku-buildpack-ruby-tpope,donnykurnia/heroku-buildpack-ruby,mattmanning/heroku-buildpack-ruby-jekyll,instacart/heroku-buildpack-ruby,ericboehs/heroku-buildpack-ruby,instacart/heroku-buildpack-ruby,Scalingo/ruby-buildpack,heroku/heroku-buildpack-ruby,Scalingo/ruby-buildpack,jonseaberg/heroku-buildpack-turbo-sprockets,mattmanning/heroku-buildpack-ruby-jekyll,andycroll/heroku-buildpack-jekyll,brightbytes/heroku-buildpack-ruby-without-assets-precompile,Genius/heroku-buildpack-ruby,qnyp/heroku-buildpack-ruby-bower,pkgr/heroku-buildpack-ruby,andycroll/heroku-buildpack-jekyll,jonseaberg/heroku-buildpack-turbo-sprockets,moneyadviceservice/heroku-buildpack-ruby-bowndler,orenyk/heroku-buildpack-ruby,ruby/heroku-buildpack-www-ruby-lang,zunda/heroku-buildpack-ruby