Added a license to the readme.

Also updated the online documentation with the license.

Author: nnnick

readme.md

@@ -5,4 +5,8 @@ Chart.js
 
 Documentation
 -------
-You can find documentation at [chartjs.org/docs](http://www.chartjs.org/docs).
+You can find documentation at [chartjs.org/docs](http://www.chartjs.org/docs).
+
+License
+-------
+Chart.js is available under the [MIT license] (http://opensource.org/licenses/MIT).