Added Cask Market availability badge

Author: bdmogal

README.md

@@ -1,6 +1,7 @@
 Dynamic Spark Plugins
 =====================
 
+![cm-available](https://cdap-users.herokuapp.com/assets/cm-available.svg)
 [![Join CDAP community](https://cdap-users.herokuapp.com/badge.svg?t=dynamic-spark)](https://cdap-users.herokuapp.com) 
 [![Build Status](https://travis-ci.org/hydrator/dynamic-spark.svg?branch=develop)](https://travis-ci.org/hydrator/dynamic-spark)
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)