create separate development and production docker builds

[senderle]

Once we have a Dockerfile that builds an image that can talk to our existing servers, we'll want to refactor it so that we can create separate development, staging, and production builds.

Initially, development and production are the most important; staging would be nice but we don't really have a staging environment right now anyway. Not having used Docker for an integrated dev + production workflow before, I'm not even sure that "staging" is a useful part of that flow, and am open to suggestions.