Add icon for coverity

Author: lefticus

index.html

@@ -57,7 +57,8 @@ <h3><i class="fa fa-microphone"></i> Free</h3>
     <div class="col-md-4">
       <h3><i class="fa fa-tachometer"></i> Stable</h3>
       <a href="https://travis-ci.org/ChaiScript/ChaiScript.svg?branch=master"><img src="https://travis-ci.org/ChaiScript/ChaiScript.png?branch=master"/></a>
-      <a href='https://coveralls.io/r/ChaiScript/ChaiScript?branch=master'><img src='https://coveralls.io/repos/ChaiScript/ChaiScript/badge.png?branch=master' alt='Coverage Status' /></a><br/><br/>
+      <a href='https://coveralls.io/r/ChaiScript/ChaiScript?branch=master'><img src='https://coveralls.io/repos/ChaiScript/ChaiScript/badge.png?branch=master' alt='Coverage Status' /></a>
+      <a href="https://scan.coverity.com/projects/5297"><img alt="Coverity Scan Build Status" src="https://img.shields.io/coverity/scan/5297.svg"/></a><br/><br/>
       ChaiScript has been making stable releases since 2009. No bugfix or feature is made without a corresponding unit test.
     </div>