Hi!

The upstream MultiMarkdown spec
<https://rawgit.com/fletcher/human-markdown-reference/master/index.html>
specifies metadata variable subsitutions, such as the following:

,--- meta.mmd
Key: value

This is the meta contents [%Key].
`---

which are not currently supported by this package:

,---
$ multimarkdown meta.mmd
Key: value<br />

<p>This is the meta contents [%Key].</p>
`---

Thanks,
Guillem