Remove maintenance mode flag from config.
Update notifications to use user ID and optionally device ID.
Update deleting Subscriptions to pass full subscription object.
Started timing requests.

Requests are all now, by default, timed using statsd, so long as a
statsd address is configured.
Add more statistics logging.

Now timing how long a request takes, how long it takes to retrieve a
user, how long it takes to retrieve a device, and how long it takes to
authenticate a request.