Created new mehods.

I had some problems with the master branch of jInvertScroll to remove the horizontal scroll behavior for my responsive site. So, I've added two public methods: 

* `reinitialize`: As it name says, it reinitialize the behavior with the previous given settings.
* `destroy`: Destroy the horizontal scroll behavior by removing `document.body` inline styles and the listeners.

Maybe it could be done much better, but its a quick way to make it work as I expected.