Add send_postatus_errors cron job

This cron job should run once a day. It'll keep an eye on postatus.txt
in production and send out an email if there are errors blocking locales
from having their strings get updated.

The use case here is that it turns out no one is watching the postatus.txt file, so some locales haven't had their strings updated in SUMO for months now. This will make sure everyone gets annoyed by emails when stuff is failing.

I'm pretty sure it works, but can't really test it totally.

I have it mailing the admins, but maybe there's a better group to email?

Anyhow, r?