Fix some readme and script bugs in examples (take 2).

I think the usual case is that you won't need sudo... Requiring it means you misconfigured something, regardless of Mac or Linux. It's also not the case that sudo doesn't ever hurt on Linux, since you might have a setup where you're in docker group but don't otherwise have unrestricted sudo.

I think I'd prefer not to use sudo by default but allow a way to override it by setting some environment variable (such as KUBE_DOCKER_NEEDS_SUDO=1).

I'd still do that as a separate PR though. At least, a separate git commit.