* Added --self-update to check for and download new versions of
the phar
* Added --only option which accepts a comma-separated list of
services to pass to docker-compose pull/up
* Added --updated option to only pass the updated services to
docker-compose pull/up
* Moved logic from entrypoint to a dedicated class.
* Disabled automatic flush of state.
* Added locking support to prevent multiple instances.
* Added logging
* Added base interface for CredentialsLoader
