Since I'm migrating away from Github, keeping the old URL in future
releases doesn't make sense.

Now distributions created from setup.py put the systemd unit file in the
correct location for units provided by packages.  It may then be enabled
and started by the user with systemctl.

Closes #11.

Since I fixed a critical bug, I think a new version number is in order.

I finally got around to learning how to make a setup.py script.  I have
finally blossomed into a mature adult.