text: Title: jwt decorator
  Body: Hi, I found an issue with `jwt_required` decorator, I don't understand why works when I used like:
  
  ```
  @custom_api.route('/resellers/<token>/registrations', methods=['GET'])
  @jwt_required
  def get_resellers(token):
    ...
  ```
  
  but NOT when:
  
  I'm using https://flask-restless.readthedocs.io/en/stable/ where I can use methods as preprocessor
  
  ```
      @classmethod
      @jwt_required
      def get_many_preprocessor(cls, search_params=None, **kw):
          print "Here not work"
  ```
  
  This worked me with `flask-jwt`, what could be?
  