The task is to generate a self-signed cert so Zulip can be started, then
to wait until Zulip is up before using certbot to generate new certs.
Zulip needs to be up so it can meet certbot's challenge. Using a deploy
hook, certs are persisted in the data directory. The same applies to
renewal.
Tweaked by tabbott mostly to edit comments remove an unnecessary
setting before merging.
Fixes#120.
