Zappadock

Exposed port 8000 to host.
Can run `python manage.py runserver 0.0.0.0:8000` to access container from host.

This release seeks to simplify Zappadock.

- Zappadock no longer validates AWS credentials, it will just mount the `~/.aws` folder and `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, `AWS_DEFAULT_REGION` and `AWS_PROFILE` environmental variables.

- Also added some instruction on adding user to docker group on Linux.

That is all.

Bug Fix:
For existing zappa projects, zappadock will use credentials based on the existing zappa_settings.json file