AUI-841 - Scroll Event Plugin

Hey Jon. This is basically a system for subscribing to scroll events for nodes. Jon Lee is going to use it in SO, and Liferay is going to use it for the GoTo MySites piece that I'm working on. Basically we can listen to scroll direction changes (up, down, left right) and scroll edges (up-edge, down-edge, etc...). We can also set a tolerence value to fire the '<direct>-edge' event when we get within a certain range of an edge. This is optional.