use newer bootstrap version

Author: cremno

_includes/header.html

@@ -4,13 +4,13 @@
         <title>{{ page.title }}</title>
 
         <!-- Latest compiled and minified CSS -->
-        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.0/css/bootstrap.min.css">
+        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
 
         <!-- Optional theme -->
-        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.0/css/bootstrap-theme.min.css">
+        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap-theme.min.css">
 
         <!-- Latest compiled and minified JavaScript -->
-        <script src="//netdna.bootstrapcdn.com/bootstrap/3.1.0/js/bootstrap.min.js"></script>
+        <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
 
         <!-- syntax highlighting CSS -->
         <link rel="stylesheet" href="/css/syntax.css">