add docutils-0.11 for testing

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist=py25,py26,py27,py31,py32,py33,pypy,du10,du09,du08,du07
+envlist=py25,py26,py27,py31,py32,py33,pypy,du11,du10,du09,du08,du07
 
 [testenv]
 deps=
@@ -48,3 +48,8 @@ deps=
 deps=
     docutils==0.10
     {[testenv]deps}
+
+[testenv:du11]
+deps=
+    docutils==0.11
+    {[testenv]deps}