Package/install/link in kubectl code

[dlorenc]

If users don't have kubectl on their path we should offer to install it somehow. We could link it into the minikube binary like monokube does or use an official build.

[luxas]

Maybe it's better to download an official build of kubectl to /usr/local/bin/ if they don't have a version of kubectl that's supported (or not at all)

[luxas]

We should at least vendor the kubectl proxy command, so we're able to run the apiserver proxy to localhost in a goroutine in minikube

[dlorenc]

Releases are available here: https://coreos.com/kubernetes/docs/latest/configure-kubectl.html

[r2d4]

Closing as we've decided not to package kubectl, but we will link it in installers when they are ready