Make event tracking work with universal analytics

Google Analytics can be included using either the classic `ga.js` code or the newer universal `analytics.js` code. Both should work with the admin template.

https://developers.google.com/analytics/devguides/collection/gajs/eventTrackerGuide
https://developers.google.com/analytics/devguides/collection/analyticsjs/events

* Update the track method to push events to both forms of the tracking code rather than just the old form