Load bootstrap.css from CDN

Author: cheton

docs/index.html

@@ -6,7 +6,8 @@
 <title>react-infinite-tree</title>
 <meta name="description" content="">
 <meta name="viewport" content="width=device-width, initial-scale=1">
-<link rel="stylesheet" href="vendor/bootstrap/3.3.6/css/bootstrap.min.css">
+<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
+<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css">
 <link rel="stylesheet" href="common.css">
 <!--[if lt IE 9]>
 <script src="//html5shiv.googlecode.com/svn/trunk/html5.js"></script>