Fixed the api version

Author: Graham Campbell

lib/Github/Client.php

@@ -82,7 +82,7 @@ class Client
         'timeout'     => 10,
 
         'api_limit'   => 5000,
-        'api_version' => 'beta',
+        'api_version' => 'v3',
 
         'cache_dir'   => null
     );