optimize for latest pointer events standard

This change updates jquery-slider to use unprefixed pointer events based on the latest [W3C spec](https://dvcs.w3.org/hg/pointerevents/raw-file/tip/pointerEvents.html).  This is supported in IE11+ and coming soon to Firefox. I left in MSPointer* support for IE10 users.  

Hopefully I got your build process correct (I ran the compress scripts for jssor.slider.js). Let me know if I missed a step.