development from docker image instead of locally

[aguang]

We want to do development from docker image instead of locally. This will remove the prerequisite of having to install various dependencies locally with pipenv right now. Uploading to the DB happens from Oscar anyway, so we only need to replicate that environment.

This would involve:

Change README.md instructions:

• Delete pipenv prereqs
• Add instructions on running Docker interactively and mounting repo files
• Change instructions for python commands to those from within Docker image

Change Dockerfile:

• To automatically create DB in addition to mysql server
• To be set up to exec into py3 container

Things to check:

• If it's possible to connect to a port from within a container