Move hyperkit driver upstream

[tstromberg]

There are currently 3 different versions of the hyperkit driver a user may have:

• Docker for Mac
• machine-drivers, when installed by brew
• minikube, when installed by curl

Let's reduce the count by 1 by upstreaming our changes. This does not mean that we should not be attempting to manage a hyperkit binary, as it's difficult to tell which one we're getting. Ours of course, is the best wink.

[afbjorklund]

https://github.com/moby/hyperkit

• https://github.com/machine-drivers/docker-machine-driver-hyperkit/tree/master/pkg/hyperkit

• https://github.com/kubernetes/minikube/tree/master/pkg/drivers/hyperkit