Markdown table support

[nico-bachner]

Pandoc uses the longtable package and environment by default, however this is overkill in most cases.

Therefore, something like this:

| Item | Price |
|------|-------|
| 1    | $20   |
| 2    | $10   |
| 3    | $40   |

should result in the following:

\begin{table}
  \centering
  \begin{tabular}[l|l]
    Item & Price \\
    \hline
    1 & $20 \\
    2 & $10 \\
    3 & $40
  \end{tabular}
  \caption{...}
  \label{...}
\end{table}

ideally with the \begin{table} \end{table} environment being optional