Add k8s external service CNAMEs (#677)

* Add external service cnames

* remove cruft

* update CI k8s version

* change CI k8s version

* min k8s ver for ext services

* trying k8s 1.5

* k8s 1.5 requires ports spec

* remove kruft

* update dns schema version

.travis/kubernetes/dns-test.yaml

@@ -183,3 +183,17 @@ spec:
   - name: c-port
     port: 1234
     protocol: UDP
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: ext-svc
+  namespace: test-1
+spec:
+  type: ExternalName
+  externalName: example.net
+  ports:
+  - name: c-port
+    port: 1234
+    protocol: UDP
+