Let's create the "latest" tag :)
Let's create the "latest" tag :)

The "latest" tag is the default tag in Docker, whenever someone
pulls `openzipkin/zipkin-cassandra`, they are pulling `latest`.
Before this change we didn't create this tag.

The refactor of `sync-quay-tags` changes its arguments from

    subminor_tag minor_tag major_tag images...
to

    reference_tag "tags to move" images...

to accomodate syncing just the `latest` tag on `zipkin-base` to
Docker Hub.

tedyoung/docker-zipkin,itszero/docker-zipkin,openzipkin/docker-zipkin,openzipkin/docker-zipkin,tedyoung/docker-zipkin,itszero/docker-zipkin,jfeltesse-mdsol/docker-zipkin,jfeltesse-mdsol/docker-zipkin