added files needed to bootstrap the project
added postgresql-client dependency to app image

this allows running the manage.py dbshell command
rely on gunicorn django integration
updated git ignore file
added files for building web frontend container
updated Makefile

- added up target to start full stack (db, app, web)
- added down target to stop full stack
- added clean target to prune images
- updated start target to create .env file and run schema migrations and
  collect static files
updated fig.yml file to include web frontend container
reorganized Makefile to clean it up
updated README file
Merge pull request #1 from ricardokirkner/basic-stack

basic stack consisting of db (postgresql), appserver (django/gunicorn) and web frontend (nginx)

- each part of the stack is run on it's own container
- containers are managed by fig
- configuration is done via environment variables