FEATURE: chrome interop

- smooths out some stuff
- adds a new function to app/lib/chrome-interop.coffee
adds a listener for onUpdated event for tabs

- load unpacked extension, then inspect background.html, open up the
  console and in the current window go to some new website, you'll see
that URL logged in the console for the background.html page of our
extension
- also, old code that logs the active tab whenever the browser action is
  invoked is still in play