Initial Dockerfile.

@malbin It's not yet done, but I'm interested in what you think!

I uploaded a pre-built image, and you can try it out by running `docker pull jagtalon/duckduckgo:v1`. It looks like it's working well, but I would really want it to sort of sync with the local filesystem so that the dev can work on her machine and the container can just pull her code in and run it. Haven't figured out yet, but this is a good start, I think.