Minikube doc updates (#802)

* Remove SecurityContextDeny from minikube instructions

Fixes #507

* Updated docs to work with minikube v0.26.0 and later

Fixes #801

- use explicit bootstrapper arg and

- also added a macOS specific startup command for easier cut-and-paste.

* Fix typo

* Switch to use `hyperkit` vm-driver instead of `xhyve` on macOS

docs/creating-a-kubernetes-cluster.md

@@ -72,7 +72,7 @@ To use a k8s cluster running in GKE:
 1.  [Install and configure
     minikube](https://github.com/kubernetes/minikube#minikube) with a [VM
     driver](https://github.com/kubernetes/minikube#requirements), e.g. `kvm2` on
-    Linux or `xhyve` on macOS.
+    Linux or `hyperkit` on macOS.
 
 1.  [Create a cluster](https://github.com/kubernetes/minikube#quickstart) with
     version 1.9 or greater and your chosen VM driver:
@@ -86,11 +86,29 @@ To use a k8s cluster running in GKE:
     certificate controller must be told where to find the cluster CA certs on
     the VM._
 
+    _Starting with v0.26.0 minikube defaults to the `kubeadm` bootstrapper, so 
+      we need to explicitly set the bootstrapper to be `localkube` for our extra-config
+      settings to work._
+
+For Linux use:
+
 ```shell
 minikube start \
   --kubernetes-version=v1.9.4 \
   --vm-driver=kvm2 \
-  --extra-config=apiserver.Admission.PluginNames=DenyEscalatingExec,LimitRanger,NamespaceExists,NamespaceLifecycle,ResourceQuota,ServiceAccount,DefaultStorageClass,SecurityContextDeny,MutatingAdmissionWebhook \
+  --bootstrapper=localkube \
+  --extra-config=apiserver.Admission.PluginNames=DenyEscalatingExec,LimitRanger,NamespaceExists,NamespaceLifecycle,ResourceQuota,ServiceAccount,DefaultStorageClass,MutatingAdmissionWebhook \
+  --extra-config=controller-manager.ClusterSigningCertFile="/var/lib/localkube/certs/ca.crt" \
+  --extra-config=controller-manager.ClusterSigningKeyFile="/var/lib/localkube/certs/ca.key"
+```
+For macOS use:
+
+```shell
+minikube start \
+  --kubernetes-version=v1.9.4 \
+  --vm-driver=hyperkit \
+  --bootstrapper=localkube \
+  --extra-config=apiserver.Admission.PluginNames=DenyEscalatingExec,LimitRanger,NamespaceExists,NamespaceLifecycle,ResourceQuota,ServiceAccount,DefaultStorageClass,MutatingAdmissionWebhook \
   --extra-config=controller-manager.ClusterSigningCertFile="/var/lib/localkube/certs/ca.crt" \
   --extra-config=controller-manager.ClusterSigningKeyFile="/var/lib/localkube/certs/ca.key"
 ```