More fixes, sync with HTML5lib

Do a better job with the wrapper <div>s added by xhtmldiff and Maruku's to_html_tree method.
More tests fixed.

vendor/plugins/maruku/lib/maruku/output/to_html.rb

@@ -157,6 +157,7 @@ Example:
 	# Render to an HTML fragment (returns a REXML document tree)
 	def to_html_tree
 		div = Element.new 'div'
+			div.attributes['class'] = 'maruku_wrapper_div'
                         children_to_html.each do |e|
                                 div << e
                         end