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/lists6.md

@@ -0,0 +1,54 @@
+## Nested
+
+*	Tab
+	*	Tab
+		*	Tab
+
+Here's another:
+
+1. First
+2. Second:
+	* Fee
+	* Fie
+	* Foe
+3. Third
+
+Same thing but with paragraphs:
+
+1. First
+
+2. Second:
+	* Fee
+	* Fie
+	* Foe
+
+3. Third
+
+
+*** Parameters: ***
+{}
+*** Markdown input: ***
+
+*** Output of inspect ***
+md_el(:document,[],{},[])
+*** Output of to_html ***
+
+*** Output of to_latex ***
+
+*** Output of to_md ***
+
+*** Output of to_s ***
+
+*** EOF ***
+
+
+
+	OK!
+
+
+
+*** Output of Markdown.pl ***
+
+
+*** Output of Markdown.pl (parsed) ***
+Error: #<NoMethodError: private method `write_children' called for <div/>:REXML::Element>