amsthm support

[tsani]

It'd be nice if I could hack pandoc a bit to get it to do something like

\begin{theorem}
    If $S$ is a convex set ...
\end{theorem}

translated to

<p class="theorem">
    If $S$ is a convex set ...
</p>

Then, all I need to do is add a theorem.css or some such to get properly formatted theorems.