[close #127] Fix LPXC Deadlock Error

LPXC can experience a deadlock error reported in #127 it was fixed in this commit:
https://github.com/ryandotsmith/lpxc/commit/1f0bd9c31324cac109a94f70589f62652b0146a3

We are vendoring those changes in in this commit
Merge pull request #128 from heroku/schneems/lpxc-fix

[close #127] Fix LPXC Deadlock Error
Clean up plugin logic and warning text

added a test
Merge pull request #126 from heroku/schneems/plugin-warnings

Clean up plugin logic and warning text
Bugfix and More tests for plugin logic
Merge pull request #132 from heroku/schneems/less-inheritance-in-plugins

Bugfix and More tests for plugin logic
Revert "Merge pull request #132 from heroku/schneems/less-inheritance-in-plugins"

This reverts commit 968736e977fcb54705d2fe2a95f11f2192026d17, reversing
changes made to 34f5f706158d55fbeabc548c5fbd0f851e547fd6.

Still some issues with this Pull Request. Going to work on it some more.
remove extra '--' from warnings
Symlink ruby.exe to ruby

Rails 4 introduced the `bin/` directory to generated projects with executables `rails`, `bundle`, `rake`, etc. The file generated on windows has a link to an incorrect `ruby.exe` in the shebang line. See #134.

This PR adds a symlink so that `ruby.exe` can be called in addition to `ruby.
should set $GEM_PATH as well for the build process

if this isn't setup properly, locally it might pick the wrong bundler
Bugfix and More tests for plugin logic

Actually testing for presence of directories now !
rails 4 plugin work

* move rails_12factor gem test to the beginning
* test against ruby 2 since that's the new default
* rails_12factor not rails_12_factor
rails 3 plugin work

* gem and plugin names are different
* rails_12factor not rails_12_factor
only warn once about plugin injection in rails 3
fix specs
use `PluginInstaller` for runtime asset compilation
set deprecation notices for runtime assets compilation
fix specs
update changelog
v78