timeline.hs: TimelineUnackcedCountsPoller: use superclass.call(...) in the constructor. This may be the better practice to implement class inheritance in JS.
busybird.css, status.tt: user.screen_name is now included in span.bb-status-username. This helps JavaScript program to locate the screen_name from DOM.
timeline.js: write API of bb.StatusesSummary object. Start writing tests for it.