COOK-3219:  Using omnibus bundler for your app is bad
  - default behavior is still unchanged
  - allow user overriding env
  - introduce "use_omnibus_ruby" true/false switch
  - complain at people doing it wrong
Merge pull request #31 from lamont-granquist/COOK-3219

COOK-3219:  Using omnibus bundler for your app is bad