perf improvements

[ehynds]

Hi, there are a couple of things you could do to improve performance of this script:

1. Don't store state as a class on the body. Hitting the DOM is expensive. Just store it in a variable, unless of course you want to expose each state to CSS.
2. Cache your jQuery selectors outside of the setInterval and for loops.

<3

[ehynds]

One more. No need to re-sort the breakpoints on each interval iteration.