Use angular-provided jqLite functions to attach / remove events

This improves IE8 compatibility: The generated events are enhanced with
methods like 'preventDefault', which are missing from native IE8 events.

As other parts of angular-focusmanager depend on these event methods,
this patch is necessary to use angular-focusmanager with IE8.
Merge pull request #1 from jannic/master

Use angular-provided jqLite functions to attach / remove events