Add donation link to docs footer.

Doc/tools/sphinxext/layout.html

@@ -8,3 +8,14 @@
     <link rel="shortcut icon" type="image/png" href="{{ pathto('_static/py.png', 1) }}" />
 {{ super() }}
 {% endblock %}
+{% block footer %}
+    <div class="footer">
+    &copy; <a href="{{ pathto('copyright') }}">Copyright</a> {{ copyright|e }}.
+    <br />
+    The Python Software Foundation is a non-profit corporation.  
+    <a href="http://www.python.org/psf/donations/">Please donate.</a>
+    <br />
+    Last updated on {{ last_updated|e }}.
+    Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> {{ sphinx_version|e }}.
+    </div>
+{% endblock %}