add version option to kubectl-minio

[jhoblitt]

When testing builds of kubectl-minio, it is difficult to demonstrate/verify which version of the plugin is installed and being used. I would like a concrete way of listing the build/version/tag similar to how kubectl version works. This information would also be useful environment state to report in github issues.

$ kubectl-minio version
Error: unknown command "version" for "minio"
Run 'minio --help' for usage.