Release Paxos version 19.0.0-alpha.10.
Release Paxos version 19.0.0-alpha.10.

 * Upgrade `avenue` to `0.6.14`.
 * Upgrade `whittle` to `0.0.2`.
 * Build with Node.js 16 on GitHub Actions.
 * Build with Node.js 16 on Travis CI.

Closes #468.

bigeasy/paxos,bigeasy/paxos