Refactor.
Update plugin authoring docs
Refactor configuration file loading - config files are now easier to override for testing purposes.

Remove mongoose db implementation (will be provided by waigo-mongo plugin instead).
Fix configuration loading.

fix package version.

Update README
Shifted test utility code into repo: waigo/test-utils
Renamed 'app' to 'application' and added shutdown() method.
App.start() does not need to return anything.
Update dependencies
Update dependencies
Minor README update.
Updated tests