Re-add chruby for managing Rubies

This PR:

- Adds a recipe for installing and managing chruby
- Sets up new LWRP actions to leverage chruby awesomeness
- :bug: fixes a bug where `.bashrc.d/*` was not executable (and thus not loaded)
- Sets the Ruby version for the omnibus user on login
- Installs rubies into `/opt/rubies` instead of hard-coding `/usr/local`