touchcancel fires a tap event

[robharper]

touchcancel should not trigger hammer events where possible, specifically tap. Only touchend should trigger a tap.
#152 noted how Android fires a touchcancel when a scroll begins. This sometimes causes a tap event to fire if the cancel happens soon enough. It is easy to cause scrolls to nearly always cause tap to fire by setting tap_max_distance: 50.

This seems to be device dependent but definitely happens on a Nexus 7 running Android 4.2.2 and Chrome 28.0.1500.94.

The fix would mean distinguishing a gesture ending on an "end" event from one ending on "cancel" and may be a hammer-wide change. @jtangelder what are your thoughts on this? I'm happy to do the PR.

[tjsmatt]

I can confirm that the same behaviour is exhibited by IE10 using touch, and just came here to open an issue about it.

My quick fix was to monkey-patch Hammer.detection.extendEventData to include a 'cancelled' property on the gesture object, which I can then check when relevant. Perhaps this would be a better approach than introducing a BC break?

[jtangelder]

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