* Untrack config.yml
`config/config.yml` has been untracked and moved to `config/config.example.yml`.
The Dockerfile has been updated to copy all `config/config.*` files and to try
to move `config/config.example.yml` to `config/config.yml`. If a user supplied
`config/config.yml` exists it is not overwritten.
* Update Dockerfile to use `shard.lock`
* Fix tests
守矢諏訪子
Mateusz Bączek