Update the release instructions.
Update the release instructions.

It's necessary to run `autogen.sh` and `configure` before each release.

thoughtbot/gitsh,thoughtbot/gitsh,andybalaam/gitsh,andybalaam/gitsh,thoughtbot/gitsh,adrianheine/gitsh,adrianheine/gitsh,jakirkham/gitsh,jakirkham/gitsh,andybalaam/gitsh,jakirkham/gitsh