Updating Ember in pass docker

Steps to update ember container in pass-docker. All steps take place in pass-docker:

1. Edit .env file to point to the right commit hash, seen in Github
2. Edit docker-compose.yml: change the tag name for the ember container. The tag for pass-ember and pass-ui-static follow the convention: <date>-<commit_hash>. This does mean that changes must already be committed to Github for the tag to accurately reflect any real info.
3. docker-compose build ember to build the thing
4. Push image to Docker Hub. docker-compose push ember. When this completes, the success message will contain the sha256 hash for the image in Docker Hub. Copy this hash (including the sha256: part) and append it to the image in the docker-compose.yml file. It should now look similar to oapass/ember:201806015-96d1830@sha256:07f8fa7c42b379f35ce88857affa992496df6f2424cff91fdce9c2c364839f4d

If for some reason you don't get a sha256 hash when pushing a new image to Docker Hub, you can find it at any time with Docker. First get the image ID using docker images. Then run the command docker inspect --format='{{index .RepoDigests 0}}' $IMAGE, where $IMAGE is the Docker image ID you just found.

Once you make the above changes, .env and docker-compose.yml should have changes. Commit those changes to a branch and submit a PR against pass-docker.