One of the challenges with Kubernetes is that it's pretty fast moving, so it's a good idea to work with resources that are up to date. I know a last commit from May doesn't seem very old but that's going to a least be missing 1.7 and could be missing 1.6 or earlier as well.
If you're interested in books on the topic, I like Kubernetes in Action (https://www.manning.com/books/kubernetes-in-action) or Kubernetes: Up and running (http://shop.oreilly.com/product/0636920043874.do)
One of the challenges with Kubernetes is that it's pretty fast moving, so it's a good idea to work with resources that are up to date. I know a last commit from May doesn't seem very old but that's going to a least be missing 1.7 and could be missing 1.6 or earlier as well.