Revert "Don't restart an app when it's being shut down"

This reverts commit 0317af702d38e50dbc8554e441f029a3a82594ed.
Update dependencies to celluloid 0.13.0 and reel 0.3.0
Stop processing socket requests when shutting down

In order to prevent apps from starting back up, especially during shutdown (but
also when being disabled), close the server socket first and then stop the
process. This prevents any new inbound connections from restarting the app.
Proxy socket connections inside app

Instead of firing off SocketProxy instances, each of which contains its own IO
reactor and assorted machinery, keep the socket proxying "in-house" inside an
app's pre-existing IO reactor. This should cut down on resource contention
issues.