Generate UMD file

[benmvp]

Hi! Thanks for this package. We just started using it at Eventbrite!

However, it just gets added to window object which is bad for module systems, especially use on the server in Node.

I was thinking about taking a crack at generating a UMD file that will work for AMD, CommonJS, as well as the current window global.

What do you think?

[olahol]

Sounds like a great a idea, if you submit a pull request I will merge it.

[benmvp]

Perfect! Thanks!