Remove runit dependency

[taoeffect]

Makes sense to do along with #4 and base this on the official alpine image.

If it helps you close this issue, I can grant you access to my private repo where I have these changes made. Just let me know.

My Dockerfile contains only these dependencies:

ENV BUILD_DEPS   build-base autoconf libevent-dev
ENV RUNTIME_DEPS libevent findutils

That's in addition to ca-certificates wget and libressl that come with my custom alpine base image.

[taoeffect]

To be clear, my fork handles periodic key rotation via Alpine's built-in cron daemon, removing the need for runit.

[jedisct1]

Runit is very useful, if only to restart jobs, see their status, avoid multiple identical jobs running simultaneously...
It's also a very tiny set of applications. So I'd rather keep it.