Update backer link

Author: marijnh

html/backers.html

@@ -40,7 +40,7 @@ <h1>List of Backers<div style="font-size: 70%"><a class="subtlelink" href="index
 
   <tr>
     <th>
-      <a href="http://twitter.com/ralphtheninja">Magnus Skog</a>
+      <a href="https://github.com/ralphtheninja">Magnus Skog</a>
     </th>
     <td class=amount>1000 €</td>
     <td class=comment></td>