Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

client-go/examples: Update CRUD Deployment sample

**What this PR does / why we need it**: 
PR motivated by [#128](https://github.com/kubernetes/client-go/issues/128), namely updating the CRUD example with the following:
- Add new step which demonstrates rolling back deployments 
- Cleanup retry loop for `Update()` steps
- Make `-kubeconfig` flag optional when running example (same as out-of-cluster example)
- Update `README.md` to reflect changes 

**Special notes for your reviewer**:
My first Kubernetes contribution- feedback very welcome!

**Release note**:

```release-note
NONE
```

/cc @ahmetb @caesarxuchao