Canonical URL and redirect to https site (fix #908)

docs/templates/shared/_head.liquid

@@ -1,8 +1,13 @@
   <head>
+    <script>
+      if ((window.location.host == "stedolan.github.io") && (window.location.protocol != "https:"))
+        window.location.protocol = "https";
+    </script>
     <meta charset="utf-8">
     <title>{{headline}}</title>
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <link rel="canonical" href="{{url}}{{permalink | remove:'/index'}}" />
     <link rel="stylesheet" href="{{root}}/bootstrap/css/bootstrap.css" type="text/css">
     <link rel="stylesheet" href="{{root}}/css/base.css" type="text/css">
     <!--[if lt IE 9]>