Add content ratings to the web app identified by by ``app_id``,
        using the specified submission id and security code.

        :returns: HttpResponse:
            * status_code (int) 201 is successful

def add_content_ratings(self, app_id, submission_id, security_code):
        """Add content ratings to the web app identified by by ``app_id``,
        using the specified submission id and security code.

        :returns: HttpResponse:
            * status_code (int) 201 is successful
        """
        url = self.url('content_ratings') % app_id
        return self.conn.fetch('POST', url,
                               {'submission_id': '%s' % submission_id,
                                'security_code': '%s' % security_code
                                })