Add STDIN as an option to `openshift kube -c`

Also cleanup examples

@bparees
It would make sense to move it `pkg/config/fixtures/` directory, similar to what we have in `pkg/build/webhook/github/fixtures/`. I guess the same problem is in `pkg/template/template_test.go` which uses `examples/guestbook/template.json`, this file exists though. Still I'd suggest creating `pkg/template/fixtures`.