- Add `d/ember-cli`, and publish port 4200
- Remove `d/sidekiq`. Sidekiq is now started with the rails server
- Move all `docker exec` logic into a single place, so we have one place to set environment variable pass-throughs
- Use `exec` for all bash scripts, so that return statuses are passed back correctly
- Avoid using `bin/bash -c` unnecessarily, because it makes escaping arguments difficult
