some fixes on the PR

see commits for details. Fixed warnings about const being redefined in rspec and fixed to work with guard and spring app preloader.

Not 100% on the what `lib/control_control.rb` does, feel free to rework the commit removing it. 
Note the `AccessDenied` class needs to be preloaded soemwhere using `require 'control_control/errors'`, this could be in the API controller i guess. Also the `require 'control_control/resource'` wasn't required to get it working with spring on app reload.