some documentation updates

--HG--
branch : trunk
diff --git a/docs/_templates/layout.html b/docs/_templates/layout.html
index 0e80308..c2add7d 100644
--- a/docs/_templates/layout.html
+++ b/docs/_templates/layout.html
@@ -41,6 +41,7 @@
     {%- if prev %}
     <link rel="prev" title="{{ prev.title|striptags }}" href="{{ prev.link|e }}">
     {%- endif %}
+    {% block extrahead %}{% endblock %}
   </head>
   <body>
     <div id="content">