Updating CONTAINERS.md documentation
Updating CONTAINERS.md documentation

I'm not well versed in Docker, however, I'm wanting to continue
to test drive the recommended community approach.  What I found
was my initial `docker-compose build` failed, and these noted
steps were the fix to get it unstuck.
samvera/hyrax,samvera/hyrax,samvera/hyrax,samvera/hyrax