Added trusted auth

Necessary because to actually use trusted auth, the core api does the following (https://github.com/woofound/core-api/blob/master/app/controllers/application_controller.rb)

      # This gives us @current_user
      if trusted_auth? && user
        @current_user = user
        return
      end

      if user && user.valid_password?(password)          # Fails (which makes sense)
        @current_user = user
      else
        if !email.blank? || !password.blank?                    # We force client to have both, so it raises UserNotFound
          raise UserNotFound
        end
      end

Currently we require either an api token or both email and password.  We should be allowing password to be blank if we're using trusted auth