Consider supporting .github directory for DEREK.yaml

GitHub supports a `.github` directory to reduce the amount of clutter in a projects root directory for [issue and contribution docs](https://github.com/blog/2111-issue-and-pull-request-templates). It would be nice if DEREK.yml could also be placed there.

A potential downside is that GitHub owns the `.github` namespace. Alternately a directory named `.automation` would be nice for this type of configuration data, but pointless if only Derek uses it.