listNotifications(options, cb) {
      options = options || {};
      if (typeof options === 'function') {
         cb = options;
         options = {};
      }

      options.since = this._dateToISO(options.since);
      options.before = this._dateToISO(options.before);

      return this._request('GET', this.__getScopedUrl('notifications'), options, cb);
   }
List the user's notifications
@see https://developer.github.com/v3/activity/notifications/#list-your-notifications
@param {Object} [options={}] - any options to refine the search
@param {Requestable.callback} [cb] - will receive the list of repositories
@return {Promise} - the promise for the http request