Introduce PeerSupervisorActor and PeerActor

**Description:** guided by the first acceptance test, this change introduces PeerSupervisorActor and PeerActor as the topmost actors for the peer nodes. Some cleanup and testing infrastructure added as as result.

Now, the acceptance test fail due to the lack of a broker to communicate to:
```
[ERROR] [03/09/2014 19:40:19.292] [default-akka.actor.default-dispatcher-4] [akka://default/user/supervisor/gateway] cannot forward message QuoteRequest(EUR) to coinffeine://fake:4790/: Failed to connect to fake:4790
com.coinffeine.common.protocol.gateway.MessageGateway$ForwardException: cannot forward message QuoteRequest(EUR) to coinffeine://fake:4790/: Failed to connect to fake:4790
```
That should be addressed on upcoming PRs.

**Testing:** TDD'ed