Changed _defaultNamespace from a property to a function so it doesn't add a superfluous <_defaultNamespace /> element to the document.
Merge branch 'master' of dev.blindacre.com:/git/projects/pagemill
Pagemill_Doctype registerTag and registerAttribute functions are public.
Parser uses looser error handling for PHP < 5.3.10.
Decode attribute values so they can be encoded by setAttribute().
Pagemill_Tag objects inherit doctype from parent where applicable. New Pagemill_Tag->replaceChild() function.