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.
TODO:
* check for a maximum extend from boundary and fire `scroll.doTouchEnd` at that point.
* eat all remaining intertial scroll events