The "latest" tag is a pain to maintain: it's a tag that we delete and
re-create at every release. Whenever we delete it, the binaries become
unavailable on Github until they are re-generated. Thus, from now on, we
conform to good practices (as examplified by the
github.com/docker/compose) project and distribute only pinned release.
The "nightly" tag remains, for now, as it allows us to distribute beta
features. It may disappear in the future.
