Add Support for Universal Analytics (analytics.js). Fixes #2.

This is my take on adding support for the new Universal Analytics library, analytics.js. I've only done some basic testing, so feedback and modifications are welcome.

I tried to standardize the event actions and event labels a bit too. The issue with this is that sometimes more than one piece of data had to be combined in the event action (if only event value would accept non-numeric values). I used [Google's documentation](https://developers.google.com/analytics/devguides/collection/gajs/eventTrackerGuide) as a loose guide for this.

I hope this helps, and thanks for a great plugin.