Add explicit license to repo

[DuaneOBrien]

While the ReadMe specifies the license as MIT/ASL2, it is good form to add the specific license texts to the repo. I am happy to submit a PR to update this.

[Frijol]

Thank you, that would be helpful! Oversight on our part.

You will also need to sign the CLA, if you haven't already: http://dojofoundation.org/about/claForm