Normalizes mouse/touch events into 'pointer' events.

This library is in the process of being re-written to support the W3C Pointer Events specification.

The following events are generated:

• pointerdown: based on mousedown/touchstart
• pointerup: based on mouseup/touchend
• pointermove: based on mousemove/touchmove
• pointerleave: based on mouseout/touchleave
• pointerclick: a 'fast click' event based on a sequence of the above events. Additional heuristics are applied to determine whether or not to generate a pointerclick.

pointer events have the following custom properties:

• maskedEvent: the event that triggered the pointer event.
• touch: boolean- is maskedEvent a touch event?
• mouse: boolean- is maskedEvent a mouse event?
• x: page-normalized x coordinate of the event.
• y: page-normalized y coordinate of the event.