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/saltbase/README.md

@@ -15,3 +15,6 @@ See more:
 * [pillar](pillar/)
 * [reactor](reactor/)
 * [salt](salt/)
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/saltbase/README.md?pixel)]()

cluster/saltbase/pillar/README.md

@@ -17,3 +17,6 @@ this directory, though, because they are written into
 ## Future work
 
 Document the current pillars across providers
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/saltbase/pillar/README.md?pixel)]()

cluster/saltbase/reactor/README.md

@@ -1,3 +1,6 @@
 [SaltStack reactor](http://docs.saltstack.com/en/latest/topics/reactor/) files, largely defining reactions to new nodes.
 
 **Ignored for GCE, which runs standalone on each machine**
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/saltbase/reactor/README.md?pixel)]()

cluster/saltbase/salt/README.md

@@ -32,3 +32,6 @@ Config                                              | GCE   | Vagrant | AWS | Az
 [static-routes](static-routes/) (vsphere only)      |       |         |     |
 [base](base.sls)                                    | M n   | M n     | M n | M n
 [kube-client-tools](kube-client-tools.sls)          | M     | M       | M   | M
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cluster/saltbase/salt/README.md?pixel)]()