cachebust style and js at build time

app/templates/mod/sort-topics.html

@@ -14,5 +14,5 @@
       <input type=submit value="Save order">
     </form>
 </div>
-<script src="/static/js/sort-topics.js"></script>
+<script src="{{ "/static/js/sort-topics.js" | cachebust }}"></script>
 {% endblock %}