Added coversity badge

Author: janithb

README.md

@@ -1,4 +1,7 @@
-[![Build Status](https://travis-ci.org/audit4j/audit4j-core.svg?branch=master)](https://travis-ci.org/audit4j/audit4j-core) [![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.audit4j/audit4j-core/badge.svg)](https://maven-badges.herokuapp.com/maven-central/org.audit4j/audit4j-core)
+[![Build Status](https://travis-ci.org/audit4j/audit4j-core.svg?branch=master)](https://travis-ci.org/audit4j/audit4j-core) [![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.audit4j/audit4j-core/badge.svg)](https://maven-badges.herokuapp.com/maven-central/org.audit4j/audit4j-core) <a href="https://scan.coverity.com/projects/audit4j-audit4j-core">
+  <img alt="Coverity Scan Build Status"
+       src="https://scan.coverity.com/projects/7973/badge.svg"/>
+</a>
 
 audit4j-core
 ============