Add a favicon

Fixes #16.

_includes/head.html

@@ -26,4 +26,18 @@
     <meta property="og:description" content="{% if page.description %}{{ page.description }}{% else %}{{ site.description }}{% endif %}">
     <meta property="og:url" content="{{ site.url }}{{ page.url }}">
     <meta property="og:site_name" content="{{ site.title }}">
+    <link rel="apple-touch-icon" sizes="57x57" href="apple-touch-icon-57x57.png">
+    <link rel="apple-touch-icon" sizes="114x114" href="apple-touch-icon-114x114.png">
+    <link rel="apple-touch-icon" sizes="72x72" href="apple-touch-icon-72x72.png">
+    <link rel="apple-touch-icon" sizes="144x144" href="apple-touch-icon-144x144.png">
+    <link rel="apple-touch-icon" sizes="60x60" href="apple-touch-icon-60x60.png">
+    <link rel="apple-touch-icon" sizes="120x120" href="apple-touch-icon-120x120.png">
+    <link rel="apple-touch-icon" sizes="76x76" href="apple-touch-icon-76x76.png">
+    <link rel="apple-touch-icon" sizes="152x152" href="apple-touch-icon-152x152.png">
+    <link rel="apple-touch-icon" sizes="180x180" href="apple-touch-icon-180x180.png">
+    <link rel="icon" type="image/png" href="favicon-192x192.png" sizes="192x192">
+    <link rel="icon" type="image/png" href="favicon-160x160.png" sizes="160x160">
+    <link rel="icon" type="image/png" href="favicon-96x96.png" sizes="96x96">
+    <link rel="icon" type="image/png" href="favicon-16x16.png" sizes="16x16">
+    <link rel="icon" type="image/png" href="favicon-32x32.png" sizes="32x32">
 </head>

apple-touch-icon.png

@@ -0,0 +1 @@
+apple-touch-icon-180x180.png