README.md: `INSTALL` -> `INSTALL.md`
Switch to RabbitMQ from Pgq

Instead of using PgQ, use RabbitMQ as the messaging system. This commit also
introduces automatic retrying of events. For information on this, please see
[Arch.md](Arch.md).
Move Arch.md to Architecture.md
Replace carton instructions with local::lib instructions.
Updating daemontools service to match production