Automate docker image publishing (latest is 4 years old !)

[yogeek]

I wanted to test the tool by using the docer image pointed in the documentation but it failed (cf. #178 )

And the I found out that the docker image has not been updated for 4 years apparently... hub.docker.com/r/gofed/cluster-capacity

It would be nice to automate the docker image build and its publishment to a registry in the CI