Added CSS styling

Hi Mikko

Cool idea, one of the guys at work picked up on it and I forked and modified your project a little bit - not sure if you are interested in these changes or want to keep things as you have them. Just thought i'd give you the option, no worries either way.

I didn't (yet) modify the bookmark.js or test.html files but i added the possibility to use any CSS style(s) the browser supports with automatic (hopefully reasonably reliable) vendor prefix adding.

My fork is here: https://github.com/neilstuartcraig/obfuscate.js

Cheers 
Neil