create umd dist build - for webpack aliasing

[mikevercoelen]

this is useful when creating aliases to improve webpack

http://survivejs.com/webpack/developing-with-webpack/optimizing-development/

[timdorr]

If someone wants to submit a PR that adds UMD support, go right ahead. I don't know what's involved, so I'm not the expert on the subject.

[Dattaya]

I'm not the expert on the subject.

Me neither, but I need that umd build, so I would like to ask someone knowledgeable to review the PR (#362).