Fix Delegate#on useCapture js docs (issue #74)

lib/delegate.js

@@ -119,7 +119,7 @@ Delegate.prototype.captureForType = function(eventType) {
  * @param {string} eventType Listen for these events
  * @param {string|undefined} selector Only handle events on elements matching this selector, if undefined match root element
  * @param {function()} handler Handler function - event data passed here will be in event.data
- * @param {Object} [eventData] Data to pass in event.data
+ * @param {boolean} [useCapture] see 'useCapture' in <https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener>
  * @returns {Delegate} This method is chainable
  */
 Delegate.prototype.on = function(eventType, selector, handler, useCapture) {