The old build system worked, but ssg adds some features while still
being simple and easy to hack on:
* set page title from the h1 tag, rather than the file name
* generate a sitemap (which we adapt to also generate a nav)
This site doesn't need a dynamic nav, but the Anarchy Planet docs site
will have a lot of rapidly changing pages and will benefit from a
dynamic nav. This way we can use the same build system for both
sites.
