Add docker for local development

[nickbeaird]

Overview: Add in docker files to run the app locally. The changes add the backend to a container, the frontend to a container, and adds a reverse proxy container to allow for redirecting to the API from the frontend within containers.

Acceptance:

• Users can run the development environment with docker-compose.
• The readme has updated information for running the application locally.

How to test:

1. Follow the directions for configuring your MONGO db in the README.md
2. Follow the directions for running the docker container in the README.md
3. Run your environment.