Load external assets with https in select2 example (#3053)

Otherwise it doesn't work if the page is loaded with http.

Author: franciscolourenco

examples/select2/index.html

@@ -4,9 +4,9 @@
     <meta charset="utf-8">
     <title>Vue.js custom directive integration example (select2)</title>
     <script src="../../dist/vue.js"></script>
-    <script src="http://code.jquery.com/jquery-2.1.4.min.js"></script>
-    <link href="http://cdnjs.cloudflare.com/ajax/libs/select2/4.0.0/css/select2.min.css" rel="stylesheet">
-    <script src="http://cdnjs.cloudflare.com/ajax/libs/select2/4.0.0/js/select2.min.js"></script>
+    <script src="https://code.jquery.com/jquery-2.1.4.min.js"></script>
+    <link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.0/css/select2.min.css" rel="stylesheet">
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.0/js/select2.min.js"></script>
     <style>
       html, body {
         font: 13px/18px sans-serif;