please add license

[bjtucker]

It would be easier for others to make use of your excellent work if you release it under an open source license. Otherwise, the code exists in a gray area where your clear intent is to share it, but you never explicitly give permission.

Please make a final commit with a license file that releases your code under an open source license for others to use and modify. I prefer the MIT license, but there are a lot available.

Thanks so much for contributing this module.