TODO

- Use Twisted for logging/debug

- Handle more errors properly

- Only run BOB tunnel creation Protocol for first Protocol created by the
  Factory, shortcut the process for subsequent Protocols.
  - Does this matter? Will a Factory ever have multiple Protocols at once?
  - For clients, the tunnel dies with the first Protocol

- If a tunnel exists and its settings match what the tunnel creator wants,
  don't stop and start the tunnel
  - Important for a server tunnel used multiple times by client endpoints,
    first client will stop the tunnel and add inport, later clients should
    not (unless the inport is explicitly specified by the client tunnel and
    does not match)

- Examine design, decide where I2P tunnels should be created and removed
  - Client and server tunnels are created by the endpoint
    - Once the tunnel is created, the real Protocol/ListeningPort is created
      and returned via a Deferred callback chain
    - Should the tunnels be created by the Protocol/ListeningPort instead?
  - Client tunnels are removed by I2PClientTunnelProtocol.connectionLost()
  - Server tunnels are removed by I2PListeningPort.stopListening()