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/html2.md

@@ -0,0 +1,38 @@
+Write a comment here
+*** Parameters: ***
+{} # params 
+*** Markdown input: ***
+One
+<div></div>123
+
+<div></div>123
+*** Output of inspect ***
+md_el(:document,[
+	md_par(["One ", md_html("<div></div>"), "123"]),
+	md_html("<div></div>")
+],{},[])
+*** Output of to_html ***
+<p>One <div />123</p>
+<div />
+*** Output of to_latex ***
+One 123
+*** Output of to_md ***
+One 123
+*** Output of to_s ***
+One 123
+*** EOF ***
+
+
+
+	OK!
+
+
+
+*** Output of Markdown.pl ***
+<p>One
+<div></div>123</p>
+
+<p><div></div>123</p>
+
+*** Output of Markdown.pl (parsed) ***
+Error: #<NoMethodError: private method `write_children' called for <div> ... </>:REXML::Element>