getRelease(id, cb) {
      return this._request('GET', `/repos/${this.__fullname}/releases/${id}`, null, cb);
   }
Get information about a release
@see https://developer.github.com/v3/repos/releases/#get-a-single-release
@param {string} id - the id of the release
@param {Requestable.callback} cb - will receive the release information
@return {Promise} - the promise for the http request