Update README.md

Added reference badge

Author: keilw

README.md

@@ -10,5 +10,6 @@ This is the API module of JSR 354 licenced under
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/javax.money/money-api-bp/badge.svg)](https://maven-badges.herokuapp.com/maven-central/javax.money/money-api-bp)
 [![Build Status](https://api.travis-ci.org/JavaMoney/jsr354-api-bp.png?branch=master)](https://travis-ci.org/JavaMoney/jsr354-api-bp)
 [![Coverage Status](https://coveralls.io/repos/JavaMoney/jsr354-api-bp/badge.svg)](https://coveralls.io/r/JavaMoney/jsr354-api-bp)
+[![Reference Status](https://www.versioneye.com/java/javax.money:money-api-bp/reference_badge.svg?style=flat)](https://www.versioneye.com/java/javax.money:money-api-bp/references)
 
 [![Built with Maven](http://maven.apache.org/images/logos/maven-feather.png)](http://maven.org/)