feat(post): deis 0.12 release

Still a WIP, especially the title. Please post feedback here and I'll update. ping @gabrtv @bacongobbler @JoshuaSchnell @carmstrong @smothiki.
Let's remove "`fleetctl` is not required now".  Until we add a `deisctl list-units` that lists _all_ units -- not just deis ones,  you might need to use `fleetctl` for exploring/managing app containers.