Add tracking pixel

Author: zackbloom

README.md

@@ -21,3 +21,6 @@ If you use AMD or Browserify, require pace.js and call `pace.start()` as early i
   <link href="/pace/themes/pace-theme-barber-shop.css" rel="stylesheet" />
 </head>
 ```
+
+[![Analytics](https://ga-beacon.appspot.com/UA-45159009-2/pace/readme)](https://github.com/igrigorik/ga-beacon?pixel)
+