Merge branch 'fig-info' into 'master'

information about why we use fig.yml

Because of tweet https://twitter.com/nicholasruunu/status/619533541605539841

cc/ @sytses @ayufan

See merge request !960

docker/README.md

@@ -163,3 +163,5 @@ sudo docker push gitlab/gitlab-ce:latest
 ## Troubleshooting
 
 Please see the [troubleshooting](troubleshooting.md) file in this directory.
+
+Note: We use `fig.yml` to have compatibility with fig and because docker-compose also supports it.