Upgrade dependencies: go-client v8.0.0, k8s v1.11

[jwkohnen]

This is not well tested, but I did the annoying work to upgrade the kubernetes go-client dependency to version 8.0.0 and adjust to the breaking changes that comes with it (mostly breaking changes that were introduced by version 5.0.0). Also I upgraded the kubernetes object's apiVersion where applicable.

I did not test it thouroughly. There seem to be bugs, but since I started using kube-prompt just today, I don't even know yet, if these bugs are related to the upgrade. But I suppose this PR is still worthwhile to move towards an up to date kubernetes client.

• Add dependency to apimachinery; use it for ListOptions

• Change code to reflect breaking changes of go-client v5.0.0:

  • Enforced explicit references to API group client interfaces in
    clientsets to avoid ambiguity.
  • Moved pkg/api and pkg/apis to k8s.io/api

  See https://github.com/kubernetes/client-go/blob/master/CHANGELOG.md#v500

• Rename package imports that have API version as their last label to
  better reflect which API they represent

• Migrate objects to newer API versions: Some k8s objects have migrated
  to newer apiVersions like apps/v1, core/v1.

[jwkohnen]

Would fix #17.

[c-bata]

Nice! I'll check later.

[jwkohnen]

I've pushed a commit that imports the GCP auth helper. I think it was not necessary to do that before, but it seems my dep upgrade broke authentication to GKE clusters. It may be necessary to include other auth helpers.

[c-bata]

This changes works fine with the kubernetes cluster which is used in our company 👍
Thanks.