Use server block defaults (#894)

* mw/k8s: Test Federation parsing

The test case was there, but there was nothing testing it?!?!?!
Add it and split it out of the main setup test which is too long
already.

Also allow kubernetes a not have a ZONE, just default to the serverblock
in that case. Remove test that was blocking that.

Cleanup up the readme more.

* rewrite README

middleware/kubernetes/setup.go

@@ -87,10 +87,6 @@ func kubernetesParse(c *caddy.Controller) (*Kubernetes, error) {
 				}
 			}
 
-			if k8s.Zones == nil || len(k8s.Zones) < 1 {
-				return nil, errors.New("zone name must be provided for kubernetes middleware")
-			}
-
 			k8s.primaryZone = -1
 			for i, z := range k8s.Zones {
 				if strings.HasSuffix(z, "in-addr.arpa.") || strings.HasSuffix(z, "ip6.arpa.") {