Removed unnecessary IE8 polyfills from the docs

goratchet.com does not work on IE8 so lets remove these polyfills.

docs/_includes/header.html

@@ -14,12 +14,6 @@
 <link rel="stylesheet" href="/dist/ratchet.min.css">
 <link rel="stylesheet" href="/assets/css/docs.min.css">
 
-<!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
-<!--[if lt IE 9]>
-  <script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
-  <script src="https://oss.maxcdn.com/libs/respond.js/1.4.2/respond.min.js"></script>
-<![endif]-->
-
 <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/assets/img/apple-touch-icon-114x114.png">
 
 <script>