`glide get` has weird dependencies on the glide cache.
`glide install` just updates `glide.lock` but doesn't update /vendor.
`glide init` will detect dependencies from your current project,
making it dependent on the external files.
Just recommend users create a `glide.yaml` manually, then use
`glide update` to populate their /vendor directory. Technically you
could do a dance of `glide init` -> `glide get` -> `glide update`[0]
but this seems less error prone.
Additionally, provide instructions for users who want to use
different versions of packages than `client-go`, and add a note
about glide-vc.
[0] https://github.com/coreos/etcd/blob/v3.1.1/scripts/updatedep.sh
