Release Mingle Kubernetes version 2.1.0.
Release Mingle Kubernetes version 2.1.0.

 * Upgrade `rescue` to `6.0.3`.
 * Upgrade `destructible` to `5.2.0-alpha.4`. Closes #222.
 * Upgrade `fastify` to `2.11.0`. Closes #221.
 * Upgrade `axios` to `0.19.1`. Closes #220.
 * Upgrade `interrupt` to `9.0.0-alpha.4`. Closes #219.
 * Revert Mingle Kubernetes tests to Proof. Closes #218.
 * Update `LICENSE`s for 2020. Closes #198.

Closes #223.

bigeasy/mingle