Show the hamburger icon on the main page

- Fixes #36
- Fixes #38
- Closes #43

Author: Vogeltak

_includes/header_light.html

@@ -43,6 +43,6 @@
         {% endif %}
       {% endfor %}
     </ul>
-    <a href="#" data-activates="nav-mobile" class="button-collapse"><i class="mdi-navigation-menu"></i></a>
+    <a href="#" data-activates="nav-mobile" class="button-collapse"><i class="mdi-navigation-menu grey-text"></i></a>
   </div>
 </nav>