README.md: Update bare-metal docs link to matchbox

* Link to the terraform-based example which is easier for newcomers

Author: dghubble

README.md

@@ -12,7 +12,7 @@ If you are interested in the design and details [see the Kubernetes self-hosted
 
 * [GCE Quickstart](hack/quickstart/quickstart-gce.md)
 * [AWS Quickstart](hack/quickstart/quickstart-aws.md)
-* [CoreOS Baremetal](https://github.com/coreos/coreos-baremetal/blob/master/Documentation/bootkube.md)
+* [Bare-Metal](https://github.com/coreos/matchbox/tree/master/examples/terraform/bootkube-install)
 * [Vagrant Single-Node](hack/single-node/README.md)
 * [Vagrant Multi-Node](hack/multi-node/README.md)