Add tinker.io to list of projects using normalize

Author: necolas

index.html

@@ -64,6 +64,7 @@ <h2>Who uses it?</h2>
                 <li><a href="http://twitter.github.com/bootstrap/">Twitter Bootstrap</a></li>
                 <li><a href="https://www.gov.uk/">GOV.UK</a></li>
                 <li><a href="http://css-tricks.com/">CSS Tricks</a></li>
+                <li><a href="https://tinker.io">Tinker.io</a></li>
             </ul>
 
             <h2>Browser support</h2>