add MIT license blurb

README.md

@@ -10,7 +10,7 @@ The easiest way to install the extension is through the Chrome Web Store:
 
 https://chrome.google.com/webstore/detail/isometric-contributions/mjoedlfflcchnleknnceiplgaeoegien?hl=en&gl=US
 
-## Developer mode
+### Developer mode
 
 If you want to hack on the extension, you'll need to install it manually. First clone or fork this repo. Then, on your Extensions page, make sure "Developer mode" is checked. You can then click the "Load unpacked extension..." button and browse to the `chrome` directory of this repo.
 
@@ -23,3 +23,7 @@ To hack on the extension, you'll first need to make sure you've installed it in
 ![](http://cl.ly/image/10370H2B2Q1G/content)
 
 Feel free to send a pull request if you've made an improvement.
+
+## License
+
+This project is licensed under the [MIT License](http://opensource.org/licenses/MIT).