Mousewheel support

Add experimental mousewheel support.

This is a simplistic port of [ftscroller](https://github.com/ftlabs/ftscroller)’s mousewheel support.
https://github.com/ftlabs/ftscroller/blob/master/lib/ftscroller.js#L2255-L2323

As such, it currently still suffers from extra delayed mousewheel bounce backs on platforms that have intertial scrolling due to mousewheel events firing throughout the native inertial scroll behavior.