doc(README.md): elaborate on standalone usage

Author: Aaron Schlesinger

README.md

@@ -10,7 +10,7 @@ This Deis component is currently in beta status, and we welcome your input! If y
 
 # About
 
-This component is a PostgreSQL database for use in the Deis open source PaaS. It builds on the official [postgres](https://registry.hub.docker.com/_/postgres/) Docker image image.
+This component is a PostgreSQL database for use in Kubernetes. It builds on the official [postgres](https://registry.hub.docker.com/_/postgres/) Docker image. While it's intended for use inside of the Deis open source [PaaS](https://en.wikipedia.org/wiki/Platform_as_a_service), it's flexible enough to be used as a standlone pod on any Kubernetes cluster.
 
 Master/slave replication and leader election code is largely inspired by [`compose/governor`](https://github.com/compose/governor).