Feature Request: configurable swipe event thresholds

[mlitwin]

There are a number of hard-coded constants in the jquery.mobile.event.js swipe code. I'm feeling the need to tweak those constants (specifically to allow a greater vertical displacement and still swipe - I'm playing around with 150 rather than the default 75, which seems to feel better at least on the iPhone).

The feature request here is to expose those constants to tweaking.

Possible implementation / patch: https://gist.github.com/1055494