restore extra_script

This fell out of the template at some point, but is needed for some
javascripty things to work.

pinaxcon/templates/site_base.html

@@ -61,6 +61,8 @@
           <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
           <script src="{{ STATIC_URL }}/js/bootstrap.min.js" type="text/javascript"></script>
           <script src="{{ STATIC_URL }}/js/jquery.formset.js"></script>
+          {% block extra_script %}
+          {% endblock %}
           {% block scripts_extra %}{% endblock %}
       {% endblock %}