v0.6-pre

Release Prep (#41)

This PR in a variety of release-oriented changes in preparation for delivering testing artifacts and moving towards more formal releases.

## Added
- Extracted `myceli` config values into config file with reasonable defaults.
- CI based docker builds and binary releases.
- Basic general testing plan in `testing/testing-plan.md`.
- Added basic for for building/running `myceli` in Docker.

## Changed
- Updated docs/readme to reflect new `myceli` configuration file.