Update e2e/README.md

Add description for each environment variable used for customizing the test cluster

e2e/README.md

@@ -42,3 +42,27 @@ KUBE_AWS_DEPLOY_TO_EXISTING_VPC=1 \
   KUBE_AWS_USE_CALICO=true \
   KUBE_AWS_CLUSTER_NAME=kubeawstest1 sh -c './run all'
 ```
+
+## Customizing your test kubernetes cluster
+
+The test cluster created by the `e2e/run` script can be customized via various environment variables.
+
+`KUBE_AWS_DEPLOY_TO_EXISTING_VPC=1`: Set to `1` if you'd like the script to provision a VPC before running kube-aws and then deploying a kubernetes cluster to it.
+
+`KUBE_AWS_CLUSTER_AUTOSCALER_ENABLED=1`: Set to `1` if you'd like to tag the resulting cloudformation stack with the sourth-of-truth for cluster-autoscaler.
+
+`KUBE_AWS_NODE_POOL_INDEX=1`: Set to an integer greater than 1 if you'd like to provision additional node pool(s).
+
+`KUBE_AWS_AWS_NODE_LABELS_ENABLED=1`: Enable the `awsNodeLabels` experimental feature by automatically modifying `cluster.yaml`.
+
+`KUBE_AWS_NODE_LABELS_ENABLED=1`: Enable the `nodeLabels` experimental feature to tag node pool(s) with example user-provided tags.
+
+`KUBE_AWS_WAIT_SIGNAL_ENABLED=1`: Enable the `waitSignal` experimental feature.
+
+`KUBE_AWS_AWS_ENV_ENABLED=1`: Enable the `awsEnvironment` experimental feature.
+
+`KUBE_AWS_USE_CALICO=true`: Enable Calico throughout the cluster.
+
+`KUBE_AWS_CLUSTER_NAME=mycluster`: The name of a kube-aws main cluster i.e. a cloudformation stack for the main cluster. Must be unique in your AWS account.
+
+