Add support to run watcher under supervisord

[stv-io]

It would be awesome if this tool could run as a service, under for example supervisord. This would mean delegating the pid management to the sub-service running the script.

Does this make sense in light of this project?

[stv-io]

ping @gregghz for your thoughts 😄

[gregghz]

That sounds like a good idea. I don't have any short term plans to implement this but I'll leave the issue open in case someone else wants to contribute the work.