code: function(type, handler) {
              var self = this,
                  proxy = function (event) {
                      self.off(type, proxy);
                      handler.call(self, event);
                  };
              proxy.handler = handler;
              this.on(type, proxy);
          }
docs: Adds a new event handler that should be removed after it's been triggered once.
  @param {string} type The name of the event to listen for.
  @param {Function} handler The function to call when the event occurs.
  @returns {void}