Merge pull request mdn#55 from j9peters/update-bootstrap-link

Update stylesheet

Author: chrisdavidmills

catalog/templates/base_generic.html

@@ -5,7 +5,7 @@
   {% block title %}<title>Local Library</title>{% endblock %}
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
-  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
+  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
   <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
   <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>