Author here.
The full guide to this post is located on Github: https://github.com/giantswarm/swarm-wercker#swacker-continuo... and the video walkthrough is on Vimeo: https://vimeo.com/134043502. The code for the Wercker step is here: https://github.com/giantswarm/giantswarm-wercker-step.
There's a good post on Wercker's site that covers pushing containers various places including Google's Container Registry: http://devcenter.wercker.com/docs/containers/pushing-contain....
