Release Kibitz version 3.0.0-alpha.18.
Release Kibitz version 3.0.0-alpha.18.

 * Upgrade `avenue` to `0.6.18`.
 * Upgrade `islander` to `5.0.0-alpha.12`.
 * Upgrade `destructible` to `7.0.0-alpha.72`.
 * Upgrade `paxos` to `19.0.0-alpha.18`.
 * Update `LICENSE` for current year.

Closes #269.

bigeasy/kibitz,bigeasy/kibitz