Add ga-beacon analytics to gendocs scripts

hack/run-gendocs.sh puts ga-beacon analytics link into all md files,
hack/verify-gendocs.sh verifies presence of link.

cluster/addons/dns/MAINTAINERS.md

@@ -1,3 +1,6 @@
 # Maintainers
 
 Tim Hockin <thockin@google.com>
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/addons/dns/MAINTAINERS.md?pixel)]()

cluster/addons/dns/README.md

@@ -72,3 +72,6 @@ SkyDNS to find.
 Kubernetes installs do not configure the nodes' resolv.conf files to use the
 cluster DNS by default, because that process is inherently distro-specific.
 This should probably be implemented eventually.
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/addons/dns/README.md?pixel)]()

cluster/addons/dns/kube2sky/README.md

@@ -23,3 +23,6 @@ example, if this is set to `kubernetes.io`, then a service named "nifty" in the
 
 '-etcd_mutation_timeout': For how long the application will keep retrying etcd 
 mutation (insertion or removal of a dns entry) before giving up and crashing.
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/addons/dns/kube2sky/README.md?pixel)]()

cluster/addons/dns/skydns/README.md

@@ -3,3 +3,6 @@
 
 This container only exists until skydns itself is reduced in some way.  At the
 time of this writing, it is over 600 MB large.
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/addons/dns/skydns/README.md?pixel)]()