Update face detection module

@@ -22,9 +22,18 @@
 	background-color: #666;
 }
 </style>
-<script type='text/javascript' src="{{url_for('static', filename='js/opencv.js')}}"></script>
 <script type='text/javascript' src="{{url_for('static', filename='js/utils.js')}}"></script>
 <script type='text/javascript'>
+
+let utils = new Utils('errorMessage');
+
+utils.loadOpenCv(() => {
+    let faceCascadeFile = '/static/js/haarcascade_frontalface_default.xml';
+    utils.createFileFromUrl(faceCascadeFile, faceCascadeFile, () => {
+        alert(faceCascadeFile);
+    });
+});
+	
 function main()
 {
 let video = document.getElementById("videoInput");
@@ -47,12 +56,8 @@ let faces = new cv.RectVector();
 let classifier = new cv.CascadeClassifier();
 var streaming = true;
 
-let utils = new Utils('errorMessage'); //use utils class
-let faceCascadeFile = "/static/js/haarcascade_frontalface_default.xml"
-utils.createFileFromUrl(faceCascadeFile, faceCascadeFile, () => {
-    alert(faceCascadeFile);
-    classifier.load(faceCascadeFile);
-});
+classifier.load('static/js/haarcascade_frontalface_default.xml');
+
 const FPS = 30;
 function processVideo() {
     try {