Fix Sphinx title underline warnings

Author: twm

doc/html5lib.rst

@@ -24,7 +24,7 @@ html5lib Package
     :show-inheritance:
 
 :mod:`serializer` Module
-----------------------
+------------------------
 
 .. automodule:: html5lib.serializer
     :members:

doc/html5lib.treewalkers.rst

@@ -10,7 +10,7 @@ treewalkers Package
     :show-inheritance:
 
 :mod:`base` Module
--------------------
+------------------
 
 .. automodule:: html5lib.treewalkers.base
     :members:
@@ -34,7 +34,7 @@ treewalkers Package
     :show-inheritance:
 
 :mod:`etree_lxml` Module
------------------------
+------------------------
 
 .. automodule:: html5lib.treewalkers.etree_lxml
     :members:
@@ -43,9 +43,9 @@ treewalkers Package
 
 
 :mod:`genshi` Module
---------------------------
+--------------------
 
 .. automodule:: html5lib.treewalkers.genshi
     :members:
     :undoc-members:
-    :show-inheritance:
+    :show-inheritance: