I was mistaken, the derivation is GPL-2 or later as well.
rake: do not create the tarball anymore.

GitHub's tags are good enough to tar up every file, even if this means
requiring users to re-generate the man pages by themselves.

This includes quite a few changes as now it's easier to generate the
gem file.
rake: merge all in one Rakefile again.
rake: ensure that the git repository is not dirty before packaging.
Update to version 1.0.8.