Closing notifications w/o jQuery

For those of us not using jQuery but trying to close a Notification after a timeout, there is a short and sweet way provided straight by the docs:
http://www.w3.org/TR/notifications/#close-steps
(HTML5 notifications expose an Event onShow)

```js
notifyShow: function (event) {
  setTimeout(function() {
    event.currentTarget.cancel();
  }, 3000);
}
```

The only needed change in order for this to work is to simply add the Event as a param to the onShowNotification fn.