Upgrade Kubernetes Python client

[AlexIoannides]

"As a ML Engineer, I would like Bodywork to support the newest version of Kuberentes possible, so that I can use Bodywork with cluster running later versions of Kubernetes."

Tasks

• Upgrade the Kubernetes Python client and check to see what versions of Kubernetes it is officially compatible with.
• Run integration tests on clusters with the lowest and highest supported versions of Kubernetes (via Minikube).
• Update the documentation with the latest supported version of Kubernetes.