Merge pull request heroku#580 from heroku/schneems/revert-bundler-1.15.0

Revert "Merge pull request heroku#569 from heroku/schneems/bundler-1.15.0"

Author: schneems

lib/language_pack/ruby.rb

@@ -16,7 +16,7 @@ class LanguagePack::Ruby < LanguagePack::Base
   NAME                 = "ruby"
   LIBYAML_VERSION      = "0.1.7"
   LIBYAML_PATH         = "libyaml-#{LIBYAML_VERSION}"
-  BUNDLER_VERSION      = "1.15.0"
+  BUNDLER_VERSION      = "1.13.7"
   BUNDLER_GEM_PATH     = "bundler-#{BUNDLER_VERSION}"
   RBX_BASE_URL         = "http://binaries.rubini.us/heroku"
   NODE_BP_PATH         = "vendor/node/bin"