Old version in README examples leads to errors

[ferm10n]

I got wrecked by #60 because I was using an old image (v1.6). It took me a while to realize that I just copied the example in the README, but the latest was at v2.0.

Maybe it'd be helpful to update the README, or setup something to update the README when a new package is released?

Or maybe even better, since there's specific k8s versions this package is compatible with, wait-for.sh could detect this and throw?

[tiljanssen]

Or just check whether the search for the active/succeeded/failed yielded any result, and if not, return an error.