Heavy refactor

Tighten up Mbus::Io API such that we only expose a few public methods.  Includes extracted configuration gem as a dependency, which allows this gem to focus on two things -- sending messages and receiving / processing messages.  There's also some spec cleanup (but very little as I tried to leave the specs alone), and some logging updates.

There's still more I'd like to do, but I think this sets us up well for updating Bunny to the latest stable version.  This will then allow us to use the Bunny library instead of the AMQP library with our CA collector processes, which will hopefully fix up our awful memory leak.