fix addNotification

If you try the boilerplate on Firefox, Chrome and the Simulator and click on addNotification nothing happens.

I have integrated the code on https://developer.mozilla.org/en-US/docs/Web/API/notification and tested.
Now on the browser cited above the notification work!

this is the new code that add for the new notification before a check of permission and after show the notification.
```
var addNotification = document.querySelector("#add-notification");
    if (addNotification) {
        addNotification.onclick = function () {
            if ("Notification" in window) {
                // Firefox OS 1.1 and higher
		
		if (Notification.permission !== 'denied') {
		    Notification.requestPermission(function (permission) {
			if(!('permission' in Notification)) {
			    Notification.permission = permission;
			}
		    });
		}
		
		if (Notification.permission === "granted") {
		    var notification = new Notification("See this", {
			body : "This is a notification"
		    });    
		}
            } 
	    else {
                // Firefox OS 1.0
                var notification = navigator.mozNotification.createNotification(
                    "See this",
                    "This is a notification"
                );
                notification.show();
            }
        };
    }
```