Bump to bundler 1.5.2 which includes parallel fix
Use instance variable instead of const for tar name
Merge pull request #199 from heroku/schneems/bundler-1.5.2

Bump to bundler 1.5.2 which includes parallel fix
bump to v91
changelog
fix stash checking for buildpack:increment
add messaging around buildpack increment success
Merge pull request #204 from heroku/fix_buildpack_increment

Fix buildpack increment
raise an error if problems detecting the bundler vendor directory
figure out slug vendor base without munging in errors
add tests for user env compile
Merge pull request #203 from heroku/stderr

Fixes #202
Refactor gem logic into BundlerWrapper

gem_is_bundled?("thin") => bundler.has_gem?("thin")

This reduces the surface area of the LanguagePack and keeps the internals of the `bundler` object lock file less exposed.
Fixed a typo

Should be rails 4
Refactor has_windows_gemfile_lock? to bundler

Hide the internals of the Gemfile lock parser from LanguagePack
Faster `gem_version`

Implement `bundler.gem_version` to be constant time lookup using a hash instead of scanning with a detect.

Checking for Gemfile.lock is redundant since we have a `NoLockfile` language pack that detects this before any other packs can be run.

Reduce the Language Pack footprint so it knows less about the internals of the lockfile parser
Update to use new class
Remove un-needed Gemfile.lock check
add bundler specs for windows Gemfile detect
Merge pull request #181 from heroku/schneems/bundle-wrapper-refactor

Schneems/bundle wrapper refactor