Adding updated bootstrap to index.html

src/index.html

@@ -9,7 +9,7 @@
   
   <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet">
   <link rel="icon" type="image/x-icon" href="favicon.ico">
-  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
+  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
   <link href="https://unpkg.com/@angular/material/prebuilt-themes/indigo-pink.css" rel="stylesheet">    <script src="systemjs.config.js"></script>
   <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
 </head>