Adding configuration for building in Docker

[mtlynch]

This adds a configuration for building citybound in Docker so that users can compile it on any OS and not worry about dependencies. Updates the CONTRIBUTING.md with instructions on how to compile using Docker.

If you configure automatic builds on Docker Cloud (free for open source projects and easy to set up), users can run Citybound in a single command without ever cloning the repo. Here's an example with my copy of the Docker image:

docker run \
  -it \
  --publish 127.0.0.1:1234:1234 \
  --publish 127.0.0.1:9999:9999 \
  --name citybound mtlynch/citybound

[joe307bad]

How would I run this and persist citybound data across container restarts?

[mtlynch]

Docker allows you to persist data in volumes. Where does citybound store its persistent data on the filesystem? I'm not sure which directory it puts it in, but you can just add the flag:

-v citybound-data:/path/to/citybounds/data

and Docker will preserve that folder across container restarts.

[joe307bad]

Thanks @mtlynch. Yes, I am wondering where citybound would store it's data that would need persisted.

[sseemayer]

There is a command line argument CITY_FOLDER which defaults to ./city.