check for the proper binstubs for Rails 4
rails 4 does not support _VERSION_ on bundle binstub
clean and cache the finalized rails 4 assets
don't print out rails plugin injection if we aren't injecting anything
warn if missing gems for Rails 4
arrow the warning
don't special case thin on rails 4
Merge branch 'master' of git://github.com/heroku/heroku-buildpack-ruby