update for universal analytics and auto cookies

From https://developers.google.com/analytics/devguides/collection/analyticsjs/domains#auto:

  "Automatic Cookie Domain Configuration simplifies cross domain
   tracking implementations by automatically writing cookies to the
   highest level domain possible when the auto parameter is used.
   When used on the domain www.example.co.uk, it will try to write
   cookies in the following order:

     1. co.uk
     2. example.co.uk
     3. www.example.co.uk

   Analytics.js will fail to write a cookie on co.uk but will succeed
   on example.co.uk. Since a cookie was succesfully written on a higher
   level domain, www.example.co.uk will be skipped"