This is something that was done in beta 3, but we are coming out with a corrected version of for beta 4.
Can you try to reference the nightly js and see if it resolved?
<link href="http://code.ionicframework.com/nightly/css/ionic.min.css" rel="stylesheet">
<script src="http://code.ionicframework.com/nightly/js/ionic.bundle.js"></script>