Added a destroy method to Freetile

Hi,

I needed to cleanly remove what **Freetile** does and I noticed the plugin didn't have a destroy method.

So here's what I've done:

* Added a destroy method to the Freetile object
* Added a method to remove the container's children inline styles
* Extracted the *window resize* & *custom event* callbacks to internal methods. Using *$.proxy*, I didn't have to change them that much.
* Inside the destroy method, I unbinded those callbacks cleanly without side effects to other plugins and used the inline style removing method as well.

Tested successfully with Chrome & Firefox under Fedora 16.

What are you using to minify the plugin's main js file ?

thanks,

Bernard