Angular strap modal popup does not showing the background

HTML

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.9/angular.min.js"></script>
<script src="https://cdn.rawgit.com/mgcrea/angular-strap/master/dist/angular-strap.min.js"></script>
<script src="https://cdn.rawgit.com/mgcrea/angular-strap/master/dist/angular-strap.tpl.min.js"></script>
<link rel="stylesheet" href="https://cdn.rawgit.com/mgcrea/angular-motion/master/dist/angular-motion.css">
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
<div class="bs-docs-section" ng-controller="ModalDemoCtrl">
    <button type="button" class="btn btn-lg btn-primary" data-animation="am-fade-and-scale" data-placement="center" bs-modal="modal">Click to toggle modal
      <br>
      <small>(using an object)</small>
    </button>
</div>

JavaScript

'use strict';

var app = angular.module('myApp', ['mgcrea.ngStrap']);



app.controller('ModalDemoCtrl', function($scope) {
    $scope.modal = {
      "title": "Title",
      "content": "Hello Modal. This is a multiline message!"
    };
});