getContents(ref, path, raw, cb) {
      path = path ? `${encodeURI(path)}` : '';
      return this._request('GET', `/repos/${this.__fullname}/contents/${path}`, {
         ref,
      }, cb, raw);
   }
Get the contents of a repository
@see https://developer.github.com/v3/repos/contents/#get-contents
@param {string} ref - the ref to check
@param {string} path - the path containing the content to fetch
@param {boolean} raw - `true` if the results should be returned raw instead of GitHub's normalized format
@param {Requestable.callback} cb - will receive the fetched data
@return {Promise} - the promise for the http request