Pull html5 shiv into local project for faster serving

Author: Munter

docs/_includes/head.html

@@ -7,7 +7,7 @@
   <link rel="shortcut icon" href="favicon.ico"/>
 
   <!--[if lt IE 9]>
-  <script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.2/html5shiv.min.js"></script>
+    <script src="js/html5shiv.min.js"></script>
   <![endif]-->
   <script src="js/ga.js"></script>
   <script src="js/avatars.js"></script>