License Promenade under MIT license

Promenade is an open project—done, as I understand it, to allow contributions from the open source community as is done in other projects. 

This PR provides a license to encourage contributions while protecting Dabo Health from liability using the MIT License. jQuery, Ruby on Rails, and many other open source projects use the MIT license. You can read more about it [here](http://choosealicense.com/licenses/mit/). There are other licenses we can use depending on our needs (encourage contributions and protect from liability; protect from third-party patents; etc.); this PR is meant to encourage discussion toward ultimately choosing one. Other widely-used open source software licenses are explained in simple terms here: http://choosealicense.com/licenses/

What do we think about this?