code: function _addListener(type, handler) {
          if (_status[type]) {
              _callHandler(handler);
          } else {
              _callbacks[type].push(handler);
          }
      }
docs: /*
  adds a callback to the list of functions to call for the specified event type
  @param {string} type - the event type to dispatch (APP_READY, EXTENSIONS_READY, HTML_READY)
  @param {function} handler - callback funciton to call when the event is triggered
  @private