Add Windows 8 pinned site tile meta tags

app/views/layouts/_head.html.haml

@@ -26,6 +26,10 @@
   = favicon_link_tag 'touch-icon-iphone-retina.png', rel: 'apple-touch-icon', sizes: '120x120'
   = favicon_link_tag 'touch-icon-ipad-retina.png',   rel: 'apple-touch-icon', sizes: '152x152'
+  -# Windows 8 pinned site tile
+  %meta{name: 'msapplication-TileImage', content: image_url('msapplication-tile.png')}
+  %meta{name: 'msapplication-TileColor', content: '#554488'}
+
   = yield :meta_tags
   = render 'layouts/google_analytics' if extra_config.has_key?('google_analytics_id')