doc: upgrade our google analytics invocation, plagiarizing
https://developers.google.com/analytics/devguides/collection/upgrade/reference/gajs-analyticsjs

Testing Done:
published to subdir http://pantsbuild.github.io/larrys-world/
opened chrome dev tools JS console, entered ga('send', 'ihavenoideawhatimdoing')
in chrome dev tools network tab, saw I fetched a gif from google, part of whose url was ihavenoideawhatimdoing

Bugs closed: 235

Reviewed at https://rbcommons.com/s/twitter/r/574/