updateNotifier (id, notifier) {
    return new Promise((resolve, reject) => {
      Vue.axios.put(`api/notifier/${id}`, notifier).then((response) => {
        resolve(response.data);
      }).catch((error) => {
        reject(error);
      });
    });
  }
Updates a notifier
@param {String} id - The unique id of the notifier to update
@param {Object} notifier - The notifier to update
@returns {Promise} Promise - A promise object that signals the completion
                             or rejection of the request.