Parse error for some matrix environment

[rgaiacs]

The amsmath package define six environments for matrix:

• matrix,
• pmatrix,
• bmatrix,
• Bmatrix,
• vmatrix,
• Vmatrix.

For bmatrix, Bmatrix and Vmatrix we got a parse error.

Steps to reproduce

• Build the parser
• Open index.html with Firefox.
• Type in the box (you can replace bmatrix with Bmatrix or Vmatrix):

\begin{bmatrix}
a_11 & a_12 \\
a_21 & a_22
\end{bmatrix}

• Press 'TAB'.

[fred-wang]

Thanks, I think that is easy to fix, one just has to ensure that the open and close environment names match:
https://github.com/fred-wang/TeXZilla/blob/master/base-commands.txt#L28
https://github.com/fred-wang/TeXZilla/blob/master/base-commands.txt#L65
https://github.com/fred-wang/TeXZilla/blob/master/TeXZilla.jison#L586

We also need unit tests for each command, that's not the case for matrix environments (issue #13)