Ensure that pages are tracked with more precision

I added [data-host] to the rows to make it easier to select a particular
host with the DOM.  This made the selectors much simplier in the tests.

I changed the moment humanizer formatter to show more accuracy.  Before
it was 'a few seconds', now it's '5 seconds'.

This also adds in a test asserting basic tracking.  I adjusted the watcher code to always start tracking a new tab in the onUpdated event.