Add a README to the pre-existing provdier

test/kubemark/pre-existing/README.md

+# Kubemark Pre-existing Provider Guide
+
+**Kubemark Master**
+- A set of Kubernetes control plane components running in a VM
+
+**Kubernetes Cluster**
+- A real Kubernetes Cluster that has master and minions. The hollow-node pods
+  are run in this cluster, but appear as nodes to the Kubemark Master
+
+## Introduction
+
+Every running Kubemark setup looks like the following:
+ 1) A running Kubernetes cluster pointed to by the local kubeconfig
+ 2) A separate VM where the kubemark master is running
+ 3) Some hollow-nodes that run on the Kubernetes Cluster from #1
+ 4) The hollow-nodes are configured to talk with the kubemark master at #2
+
+When using the pre-existing provider, the developer is responsible for creating
+#1 and #2.  Therefore, the kubemark scripts will not create any infrastructure
+or start a kubemark master like in other providers. Instead, the existing
+resources provided by the VM at $MASTER_IP will serve as the kubemark master.
+
+## Use Case
+
+The goal of the pre-existing provider is to use the kubemark tools with an
+existing kubermark master. It's meant to provide the developer with
+additional flexibility to customize the cluster infrastructure and still use
+the kubemark setup tools.  The pre-existing provider is an **advanced** use
+case that requires the developer to have knowledge of setting up a kubemark
+master.
+
+## Requirements
+
+To use the pre-existing provider, the expectation is that there's a kubemark
+master that is rechable at $MASTER_IP. The machine that the kubemark master is
+on has to be ssh able from the host that's executing the kubemark scripts. And
+the user on that machine has to be 'kubernetes'.
+
+Requirement checklist:
+- Set MASTER_IP to ip address to the kubemark master
+- The host where you execute the kubemark scripts must be able to ssh to
+  kubernetes@$MASTER_IP
+
+## Example Configuration
+
+_test/kubemark/cloud-provider-config.sh_
+
+```
+CLOUD_PROVIDER="pre-existing"
+KUBEMARK_IMAGE_MAKE_TARGET="push"
+CONTAINER_REGISTRY=docker.io
+PROJECT="rthallisey"
+MASTER_IP="192.168.121.29:6443"
+```