Nice handling of stickies bigger than the current window

This pull adds proper handling of stickies bigger than the window. You can scroll them with the window, until the edge is encountered - than they stick on that edge. If you reverse scrolling, they will unstick - until another edge is encountered.

__From what I know - this will make this plugin one-of-a-kind__ :) And will enable people to stick long navigation lists properly!

I had to break backwards compatibility a bit - items are positioned using 'top' (or margin-top) - and that means they have to be set absolute in css. There are two options `overflow` and `topProperty`, which can be set to false to make it 100% BC.