Update to latest HTML5lib, Add Maruku testdir

Sync with the latest html5lib.
Having the Maruku unit tests on-hand may be useful for debugging; so let's include them.

vendor/plugins/maruku/tests/unittest/attributes/default.md

@@ -0,0 +1,38 @@
+This shows the use of default attributes list.
+*** Parameters: ***
+{}
+*** Markdown input: ***
+Paragraph2 
+{#2}
+
+{paragraph}: .maruku-par
+
+*** Output of inspect ***
+md_el(:document,[
+	md_par(["Paragraph2"], [[:id, "2"]]),
+	md_el(:ald,[],{:ald=>[[:class, "maruku-par"]],:ald_id=>"paragraph"},[])
+],{},[])
+*** Output of to_html ***
+<p class='maruku-par' id='2'>Paragraph2</p>
+*** Output of to_latex ***
+Paragraph2
+*** Output of to_md ***
+Paragraph2
+*** Output of to_s ***
+Paragraph2
+*** EOF ***
+
+
+
+	OK!
+
+
+
+*** Output of Markdown.pl ***
+<p>Paragraph2 
+{#2}</p>
+
+<p>{paragraph}: .maruku-par</p>
+
+*** Output of Markdown.pl (parsed) ***
+Error: #<NoMethodError: private method `write_children' called for <div> ... </>:REXML::Element>