createIssue(issueData, cb) {
      return this._request('POST', `/repos/${this.__repository}/issues`, issueData, cb);
   }
Create a new issue
@see https://developer.github.com/v3/issues/#create-an-issue
@param {Object} issueData - the issue to create
@param {Requestable.callback} [cb] - will receive the created issue
@return {Promise} - the promise for the http request