Update README.md

Added MavenCentral badge

Author: keilw

README.md

@@ -7,8 +7,8 @@ This is the API module of JSR 354 licenced under
 - the JSR Spec Licence for Evaluation (see *EVALUATION-LICENCE.txt)
 - the JSR Spec Licence for Implementation (see *IMPLEMENTATION-LICENCE.txt)
 
+[![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)
 
 [![Built with Maven](http://maven.apache.org/images/logos/maven-feather.png)](http://maven.org/)