Support Apache-style SSI

[thany]

Would be a nice idea to support Apache-style serverside includes? That way, it's super easy to migrate projects that use SSI, from forcing my fellow developers to install and config Apache (or nginx, which uses an almost identical syntax), to having them type serve :)

Example for good measure:

<!--#include virtual="inc/bottom.html"-->

This would include ./inc/bottom.html relative to the file being processed.

Actually I believe there is an actively-being-developed module for NPM, and a gem (no idea about the status) that handle resolving these SSI.