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/math/syntax.md

@@ -0,0 +1,46 @@
+LaTeX preamble: preamble.tex
+CSS: math.css
+
+Here are some formulas:
+
+*	$\alpha$
+*	$x^{n}+y^{n} \neq z^{n}$
+
+Some inline maths: $\sum_{n=1}^\infty \frac{(-1)^n}{n} = \ln 2$. 
+
+Some display  maths:
+
+\[ \sum_{n=1}^\infty \frac{1}{n} \]
+\[ \sum_{n=1}^\infty \frac{1}{n} \text{ is divergent, but } \lim_{n \to \infty} \sum_{i=1}^n \frac{1}{i} - \ln n \text{ exists.} \]     (a)
+
+Some random AMSTeX symbols - thanks to Robin Snader for adding these:
+
+$$ \beth \Subset \bigtriangleup \smallsmile \bumpeq \ggg \pitchfork $$ 
+
+Note that $\hat g$ , $J$, and $\gamma_1\gamma_2$ all restrict to
+
+$x_1 \overline{x_2} \oplus x_2 \overline{x_1}$ and that this module
+is linear in $x_1$ and $x_2$.
+
+See label \eqref{a}.
+
+$$ \href{#hello}{\alpha+\beta} $$
+
+## Cross references ##
+
+The following are 4 equations, labeled A,B,C,D:
+
+$$ \alpha $$ (A)
+
+\[ 
+	\beta
+\] (B) 
+
+$$ \gamma \label{C} $$
+
+\[ 
+	\delta \label{D}
+\]
+
+You can now refer to (eq:A), (eq:B), \eqref{C}, \eqref{D}.
+