Added a license.

Author: Dmitriy Navrotskyy

README.md

@@ -1022,4 +1022,8 @@
     + [Subtle Patterns](http://subtlepatterns.com/)
 
 
-	
+## License
+
+<a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by/4.0/88x31.png" /></a><br />This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</a>.
+
+Please provide a link back to this repository. This is not necessary for GitHub forks.