docker-compose.yml: Upgrade project setup
docker-compose.yml: Upgrade project setup

- Upgrade to latest docker-compose format
- Change to PostgreSQL 9.6 (from 9.4)
- Use a data volumes instead of a data container
- Remove links and use docker networks for internal communication

donnex/django-docker-coookiecutter,donnex/django-docker-coookiecutter,donnex/django-docker-coookiecutter