editComment(comment, body, cb) {
      return this._request('PATCH', `/gists/${this.__id}/comments/${comment}`, {body: body}, cb);
   }
Edit a comment on the gist
@see https://developer.github.com/v3/gists/comments/#edit-a-comment
@param {number} comment - the id of the comment
@param {string} body - the new comment
@param {Requestable.callback} [cb] - will receive the modified comment
@return {Promise} - the promise for the http request