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/html4.md

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+Write a comment here
+*** Parameters: ***
+{} # params 
+*** Markdown input: ***
+<div class="frame">
+	<a  class="photo" href="http://www.flickr.com/photos/censi/54757256/"><img alt=""
+  moz-do-not-send="true"
+  src="http://static.flickr.com/27/54757256_1a2c1d2a95_m.jpg" /></a>
+</div>
+
+
+*** Output of inspect ***
+md_el(:document,[
+	md_html("<div class=\"frame\">\n\t<a  class=\"photo\" href=\"http://www.flickr.com/photos/censi/54757256/\"><img alt=\"\"\n  moz-do-not-send=\"true\"\n  src=\"http://static.flickr.com/27/54757256_1a2c1d2a95_m.jpg\" /></a>\n</div>")
+],{},[])
+*** Output of to_html ***
+<div class='frame'>
+	<a href='http://www.flickr.com/photos/censi/54757256/' class='photo'><img src='http://static.flickr.com/27/54757256_1a2c1d2a95_m.jpg' moz-do-not-send='true' alt='' /></a>
+</div>
+*** Output of to_latex ***
+
+*** Output of to_md ***
+
+*** Output of to_s ***
+
+*** EOF ***
+
+
+
+	OK!
+
+
+
+*** Output of Markdown.pl ***
+<div class="frame">
+    <a  class="photo" href="http://www.flickr.com/photos/censi/54757256/"><img alt=""
+  moz-do-not-send="true"
+  src="http://static.flickr.com/27/54757256_1a2c1d2a95_m.jpg" /></a>
+</div>
+
+*** Output of Markdown.pl (parsed) ***
+Error: #<NoMethodError: private method `write_children' called for <div> ... </>:REXML::Element>