Don't omit optional tags by the default in the serializer.

gsnedders · gsnedders · commit 601fe173b183 · 2014-05-19T15:29:17.000+01:00
It is only safe to omit optional tags when we know the document is conforming,
and the content model restrictions are obeyed.
diff --git a/html5lib/serializer/htmlserializer.py b/html5lib/serializer/htmlserializer.py
@@ -82,7 +82,7 @@ class HTMLSerializer(object):
     use_best_quote_char = True
 
     # tag syntax options
-    omit_optional_tags = True
+    omit_optional_tags = False
     minimize_boolean_attributes = True
     use_trailing_solidus = False
     space_before_trailing_solidus = True
