figure out a reasonable swipe distance and tolerance for swipe events

[scottjehl]

Currently, we have to move 180px horizontally, which is far more than other frameworks require.

jQtouch uses a horizontal distance of 35px. I found some native xcode examples that say 25px.
Maybe 30px ish would be nice?

Also, our vertical tolerance is probably a lot larger than necessary too (80px). Maybe closer to 20px would be reasonable.

[scottjehl]

fixed in 517e070