added multi-touch gestures

More work needed here, but wanted to get some initial feedback.

I tested with two finger pinch, zoom, and pan and this works fine.

Issues here:
1. eventWithTouch was duplicated to make eventWithTouches, they should be merged.
2. dragPointsAlongPaths take an NSArray, not a CGPoint[] array. I can convert the old function to use NSArray(which I think is preferable), or, convert my code to use CGPoint[].
3. dragPointsAlongPaths assumes that all touches happen at the same time, and end at the same time. After looking at KIFEventProxy, I became less confident that this will work for arbitary lengths and touches.
4. Tests? What is the best way to write them? Some input would be nice.