Show backtrace and bail out hard on panic

Update rubocop

And use settings from sgx-jmp

Exit after an error in EM

Do not wait to exit until after we are ready

Do not hang forever if shutdown fails

Wait until fully disconnected before EM.stop

Fix intermittent notification non-delivery

We need to wait until all EventMachine items in flight are complete before we
allow the process to terminate or some of them might not happen.  So when the
process wants to exit, wait until the EM thread is done.  Use next_tick to make
sure our stop command only happens when the EM queue is next clear.

Higher XMPP connect timeout

Because sometimes the box is under high load.

Notify customer when renewal fails due to low balance

This is done by sending from a configured JID to <tel>@cheogram.com in order to
have them receive a message from support.