remove useless www.

doc/templates/layout.html

 {% extends "!layout.html" %}
 {% set script_files = script_files + ["_static/togglediv.js"] %}
 {% block rootrellink %}
-    <li><a href="http://www.kwant-project.org/">
+    <li><a href="http://kwant-project.org/">
         <img src="{{ pathto('_static/kwant_logo.png', 1) }}"
         style="vertical-align: middle; margin-top: -4px" alt="Kwant logo"/></a>
       {{ reldelim1 }}</li>