Fix error when hooks files/dirs don't exist

We had been relying on `hooks/pre-up` and `hooks/post-up` files to
exist. This explicitly checks first.

Fixes #34.
Add sigil (`$`) for symlinked dir for lsrc -F

The `$` sigil in `-F` indicates that the directory is symlinked instead
of recurred upon.

Fixes #37.
Add install instruction on Gentoo-based systems

Add instruction how to install rcm on a Gentoo-based GNU/Linux
distribution. Currently the overlay is maintained by Anton Ilin
(bronislav).
Overhaul the docs for the release target

The release targets better and more accurately document how to build
the system and how things connect.
Change the maintainer to myself at work
Move Arch into gh-pages

This doesn't need to be in the repo, so out it goes!

Also noticed that this all depends on the `gh-pages` branch.