Merge pull request #747 from kubecost/dwbrown-readme

Drop now optional requirements...

README.md

@@ -18,9 +18,8 @@ Here is a summary of features enabled by this cost model:
 ## Requirements
 
 - Kubernetes version 1.8 or higher
-- kube-state-metrics
-- Node exporter
 - Prometheus
+- kube-state-metrics (optional) 
 
 ## Getting Started