touch devices support

angular-parallax should not disable itself on both desktops with touch displays and mobile touch devices.
Angularjs fails to compile duParallax with an error `angular cannot read property 'compile' of undefined` if user has modern display with touch-interface.

This PR enables parallax for both desktops with touch interfaces and ipads. Tested on windows with touch screen display and on ipad with iOS 7.1.1.