Adding Licence

Hey, 

We really love your project and want to use it on one of our projects however our legal team is stopping us because it doesn't have a licence. You mentioned in the readme "Forking, hacking, tearing apart of this module welcome - it still needs some cleaning up", would it be possible to declare this in legal parlance i.e. adding a licence? 

This PR adds the MIT licence which allows anyone to do what they want with it and it the same as [KSS uses](https://github.com/kneath/kss/blob/master/LICENSE)

I hope you can help us use your awesome library!

Thanks,
James