Multi-touch gesture support using Event.js

Please review this initial version. Only the pinch gesture is being handled at the moment. The structure needs to be changed if you want to offer this as an optional module. I'd like to help out more with this feature, I'm just unsure of how you want to proceed with this, especially with regards to pulling this out as an optional module (e.g. we'd need hooks in the event initialization code for that to be possible?).