Merge pull request #123 from googleprivate/docs/webhook-requirements

Add MutatingAdmissionWebhook requirements to README

README.md

@@ -14,8 +14,14 @@ This software is currently alpha, and subject to change. Not to be used in produ
 - Client SDKs for integration with dedicated game servers to work with Agones.
 
 ## Requirements
-- Requires a Kubernetes cluster of version 1.9+
-- Open the firewall access for the range of ports that Game Servers can be connected to in the cluster.
+- Kubernetes cluster version 1.9+
+    - [Minikube](https://github.com/kubernetes/minikube) and [Google Kubernetes Engine](https://cloud.google.com/kubernetes-engine/) have been tested  
+    - If you are creating and managing your own Kubernetes cluster, the 
+    [MutatingAdmissionWebhook](https://kubernetes.io/docs/admin/admission-controllers/#mutatingadmissionwebhook-beta-in-19) 
+    admission controller is required.  
+    We also recommend following the
+    [recommended set of admission controllers](https://kubernetes.io/docs/admin/admission-controllers/#is-there-a-recommended-set-of-admission-controllers-to-use).
+- Firewall access for the range of ports that Game Servers can be connected to in the cluster.
 - Game Servers must have the [project SDK](sdks) integrated, to manage Game Server state, health checking, etc.
 
 ## Installation