Create an "isDisabled" flag + enable() and disable() functions to swipe.js

When writing for touch devices, occasionally you need to keep an eye on touch events that may overlap with each other. In one case, I wanted to have a pinch-to-zoom image overlayed on top of the swipe area. So I needed a way to temporarily disable swipe.js.

Please pardon the "debounced window resize" commits. They cancel eachother out (one is a revert from the other).