Implement logging

[drwallace]

I don’t see any code for logging conversations. There is a function “recap” that will “send all messages sent so far in the round to the client” but that’s only one side of the log. Because the program has a propensity to crash, it might make sense to save the state of conversations completed up to crash-time.

[jhudsy]

I'm leaving this issue open for now as it'll take me a bit too long to write appropriate code to write and read the state (given the nature of the protocol) in a sane way and there are other issues that I need to fix first.