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/encoding/utf-8.md

@@ -0,0 +1,33 @@
+Write a comment abouth the test here.
+*** Parameters: ***
+{:italian=>"\303\240\303\250\303\254\303\262\303\271."}
+*** Markdown input: ***
+Italian: àèìòù.
+
+Japanese: マルク
+
+*** Output of inspect ***
+md_el(:document,[md_par(["Japanese: \343\203\236\343\203\253\343\202\257"])],{},[])
+*** Output of to_html ***
+<p>Japanese: マルク</p>
+*** Output of to_latex ***
+Japanese: マルク
+*** Output of to_md ***
+Japanese: マルク
+*** Output of to_s ***
+Japanese: マルク
+*** EOF ***
+
+
+
+	OK!
+
+
+
+*** Output of Markdown.pl ***
+<p>Italian: àèìòù.</p>
+
+<p>Japanese: マルク</p>
+
+*** Output of Markdown.pl (parsed) ***
+Error: #<NoMethodError: private method `write_children' called for <div> ... </>:REXML::Element>