Add firewall rule to allow pods access to PodCIDR

This fixes issue #88 to allow pods access to PodCIDR such as the case of
DNS. When pods come up with an IP address in the cluster CIDR range,
they cannot access kubedns without a firewall rule to enable it. This
would also prevent pods from accessing each other depending on the
application.

docs/01-infrastructure-gcp.md

@@ -63,6 +63,13 @@ gcloud compute firewall-rules create kubernetes-allow-internal \
   --source-ranges 10.240.0.0/24
 ```
 
+```
+gcloud compute firewall-rules create kubernetes-allow-internal-podcidr \
+    --allow tcp:0-65535,udp:0-65535,icmp \
+    --network kubernetes \
+    --source-ranges 10.200.0.0/16
+```
+
 ```
 gcloud compute firewall-rules create kubernetes-allow-rdp \
   --allow tcp:3389 \