Add support for Rails 4 strong_parameters

This brings support for Rails 4 StrongParameters changes.

- Parameter sanitizing is setup for Devise controllers via
  resource_params except Omniauth Callbacks which doesn't use
  resource_params.

- Change #build_resource to not call resource_params for get requests.
  Parameter sanitizing is only needed when params are posted to the
  server so there's no need to try to construct resource params on get
  requests (new, edit).
Fix internal helper test referencing resource_params