docker-compose build command line in README.md is incorrect.

[stevenjswanson]

You have

SLURM_TAG=slurm-19-05-2-1 IMAGE_TAG=19.05.2 docker-compose build

But I think you need to use --build-arg to set those variable so they are used by Dockerfile

[giovtorres]

You would use --build-arg when using the docker CLI. However, when using docker-compose, prefixing the command with these environment variables passes it into the docker-compose.yml file here, for example. The docker-compose.yml file has defaults which you can override at runtime.