Relicense schema under MIT license
As discussed at http://xbiblio-devel.2463403.n2.nabble.com/MIT-license-as-default-for-CSL-software-tp7579193p7579395.html, it probably makes sense to relicense all the versions of the CSL schema under a more permissible license. Bruce, Simon, and I have agreed on the MIT license.
Frank agrees, too.
We currently claim copyright in 3 files: https://github.com/citation-style-language/schema/search?utf8=%E2%9C%93&q=copyright&type=
I think we can add an MIT license to the entire repo using the standard GitHub template. Will prep a PR.
(leaving this open since we'll probably want to backport the MIT license to at least CSL 1.0.1)