R1:a1e7a4ccca0c

Version the Aphlict notification server and prompt users to upgrade if they're out of date

Summary: Ref T4324. Add some version information to the server status output, and setup checks to test for an unreachable or out-of-date server.

Test Plan:
- With server down, hit reasonable setup check.
- With server up and at a bad version, hit reasonable setup check.
- Viewed `/notification/status/`.
- The CSS thing fixes this:

{F114445}

Reviewers: btrahan, chad

Reviewed By: chad

CC: chad, aran…