Added broadcasting of permission events on state change and corresponding tests

This pull request adds the broadcasting of two events:

$stateChangePermissionAccepted is broadcasted when one of the permissions is accepted and
$stateChangePermissionDenied when no suitable permission has been found. My use case is to listen for this event and notify the user via a toast message.

I've also added some tests for this which has the benefit that there now are some tests for the permission.mdl.js

The README.MD has also been updated.

Feel free to rename the events / add more stuff to the readme etc.