Feature/omniauthhelper rehash

- Fixed #20 by rewriting OmniAuthHashHelper and OmniAuthHelper into `lib/login/omni_auth_hash_manager/validator.rb` and `mapper.rb`
- Full coverage for this new strategy
- Rewrote old tests to work in new strategy
We'll want to do a sanity check on OAuth2 App creation specifically to test our Doorkeeper configuration.

     Create an OAuth2 Application
     Scenario: As a logged out user
        Presented with login screen
     Scenario: As a logged in user that has admin rights
         Should be able to create an application
     Scenario: As a logged in user without admin rights
         Should be redirected somewhere else