Adds Docker Image v1 Spec Documention

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)
How about we use `example.com/busybox:v1.0.0`? I now realize that this specification doesn't even begin to describe the canonical format for image names. This needs to be added too.