Update DNS readme to point to the new code repository

cluster/addons/dns/README.md

 # kube-dns
-kube-dns schedules DNS Pods and Service on the cluster, other pods in cluster can
-use the DNS Service’s IP to resolve DNS names.
 
-More details on http://kubernetes.io/docs/admin/dns/.
+`kube-dns` schedules DNS Pods and Service on the cluster, other pods in cluster
+can use the DNS Service’s IP to resolve DNS names.
+
+* [Administrators guide](http://kubernetes.io/docs/admin/dns/)
+* [Code repository](http://www.github.com/kubernetes/dns)
 
 ## Manually scale kube-dns Deployment
+
 kube-dns creates only one DNS Pod by default. If
 [dns-horizontal-autoscaler](../dns-horizontal-autoscaler/)
 is not enabled, you may need to manually scale kube-dns Deployment.
@@ -14,27 +17,28 @@ Please use below `kubectl scale` command to scale:
 kubectl --namespace=kube-system scale deployment kube-dns --replicas=<NUM_YOU_WANT>
 ```
 
-Do not use `kubectl edit` to modify kube-dns Deployment object if it is controlled by
-[Addon Manager](../addon-manager/). Otherwise the modifications will be clobbered,
-in addition the replicas count for kube-dns Deployment will be reset to 1. See
-[Cluster add-ons README](../README.md) and [#36411](https://github.com/kubernetes/kubernetes/issues/36411)
-for reference.
+Do not use `kubectl edit` to modify kube-dns Deployment object if it is
+controlled by [Addon Manager](../addon-manager/). Otherwise the modifications
+will be clobbered, in addition the replicas count for kube-dns Deployment will
+be reset to 1. See [Cluster add-ons README](../README.md) and
+[#36411](https://github.com/kubernetes/kubernetes/issues/36411) for reference.
 
 ## kube-dns Deployment and Service templates
 
-This directory contains the base UNDERSCORE templates that can be used
-to generate the kubedns-controller.yaml.in and kubedns.controller.yaml.in needed in Salt format.
+This directory contains the base UNDERSCORE templates that can be used to
+generate the kubedns-controller.yaml.in and kubedns.controller.yaml.in needed in
+Salt format.
 
 Due to a varied preference in templating language choices, the transform
-Makefile in this directory should be enhanced to generate all required
-formats from the base underscore templates.
+Makefile in this directory should be enhanced to generate all required formats
+from the base underscore templates.
+
+**N.B.**: When you add a parameter you should also update the various scripts
+that supply values for your new parameter.  Here is one way you might find those
+scripts:
 
-**NOTE WELL**: Developers, when you add a parameter you should also
-update the various scripts that supply values for your new parameter.
-Here is one way you might find those scripts:
 ```
-cd kubernetes
-find [a-zA-Z0-9]* -type f -exec grep kubedns-controller.yaml \{\} \; -print -exec echo \;
+cd kubernetes && git grep 'kubedns-controller.yaml'
 ```
 
 ### Base Template files
@@ -42,17 +46,23 @@ find [a-zA-Z0-9]* -type f -exec grep kubedns-controller.yaml \{\} \; -print -exe
 These are the authoritative base templates.
 Run 'make' to generate the Salt and Sed yaml templates from these.
 
+```
 kubedns-controller.yaml.base
 kubedns-svc.yaml.base
+```
 
 ### Generated Salt files
 
+```
 kubedns-controller.yaml.in
 kubedns-svc.yaml.in
+```
 
 ### Generated Sed files
 
+```
 kubedns-controller.yaml.sed
 kubedns-svc.yaml.sed
+```
 
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