Add option to use pod name rather than IP address for Kubernetes (#1190)

Change to use a new 'endpoints' directive and use a constant

Add initial docs for 'endpoints' directive

Add tests to Kubernetes setup for endpoints

Changes based on PR feedback

endpoint_pod_names is a boolean config option. Chahanged docs to reflect this.

Add a test when endpoints_pod_names is not set

Update README.md

Remove endpointNameModeName as it is no longer used

plugin/kubernetes/setup.go

@@ -104,6 +104,13 @@ func kubernetesParse(c *caddy.Controller) (*Kubernetes, dnsControlOpts, error) {
 
 		for c.NextBlock() {
 			switch c.Val() {
+			case "endpoint_pod_names":
+				args := c.RemainingArgs()
+				if len(args) > 0 {
+					return nil, opts, c.ArgErr()
+				}
+				k8s.endpointNameMode = true
+				continue
 			case "pods":
 				args := c.RemainingArgs()
 				if len(args) == 1 {