Install docs: minikube 0.25.2 and k8s 1.9.4

More work to try and avoid confusion, given that
minikube seems to be having issues lately.

docs/installing_agones.md

@@ -144,6 +144,10 @@ a virtualisation solution, such as [VirtualBox][vb] as well.
 [minikube]: https://github.com/kubernetes/minikube#installation
 [vb]: https://www.virtualbox.org
 
+> Note: due to some [issues with the 0.26.x release](https://github.com/GoogleCloudPlatform/agones/issues/192), 
+we recommend installing version [0.25.2 of minikube](https://github.com/kubernetes/minikube/releases/tag/v0.25.2)
+until they are resolved.
+
 ## Creating an `agones` profile
 
 Let's use a minikube profile for `agones`.
@@ -154,10 +158,11 @@ minikube profile agones
 
 ## Starting Minikube
 
-The following command starts a local minikube cluster via virtualbox.
+The following command starts a local minikube cluster via virtualbox - but this can be
+replaced by a [vm-driver](https://github.com/kubernetes/minikube#requirements) of your choice.
 
 ```bash
-minikube start --kubernetes-version v1.9.0 --vm-driver virtualbox \
+minikube start --kubernetes-version v1.9.4 --vm-driver virtualbox \
   --extra-config=apiserver.Admission.PluginNames=NamespaceLifecycle,LimitRanger,ServiceAccount,PersistentVolumeLabel,DefaultStorageClass,DefaultTolerationSeconds,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,ResourceQuota \
   --extra-config=apiserver.Authorization.Mode=RBAC
 ```