Document release process.

Fixes #292.

This is mostly an initial sketch for discussion.

This also at least partially addresses #86, #87, #126, #277.
> Why this change? Both paths seem to exist and are actually symlinks to `xtables-multi`

On current fedora, /sbin is a link to /usr/sbin, and the package
provides /usr/sbin/iptables. I was using repoclosure to see if all the
dependencies were satisfied, and /sbin/iptables was one that wasn't.