Add a script suitable for wget https://get.k8s.io | sh installation

Unsure about this. It probably won't "just work" because they'll need to set up gcloud. So, I suggest just dumping them in the kubernetes directory, and print out a help message:

```
Installed!
* to launch a cluster, type: cluster/kube-up.sh
* to tear down your cluster, type: cluster/kube-down.sh
* to see how to run commands on your cluster, use `cluster/kubectl.sh --help`
```