Add PE Level 2 twist and tangentialPressure props

See https://w3c.github.io/pointerevents/#dom-pointerevent-twist and
https://w3c.github.io/pointerevents/#dom-pointerevent-tangentialpressure

Closes gh-344

Author: patrickhlauke

src/PointerEvent.js

@@ -85,6 +85,8 @@ function PointerEvent(inType, inDict) {
   e.pressure = pressure;
   e.tiltX = inDict.tiltX || 0;
   e.tiltY = inDict.tiltY || 0;
+  e.twist = inDict.twist || 0;
+  e.tangentialPressure = inDict.tangentialPressure || 0;
   e.pointerType = inDict.pointerType || '';
   e.hwTimestamp = inDict.hwTimestamp || 0;
   e.isPrimary = inDict.isPrimary || false;