[blink1] Move blink1.js to the background page

Moving `blink1.js` to the background page gives me the ability to disconnect the device properly when main window is closed.
In order to keep the app simple, I've arbitrarily decided to have only one unique window opened at a time. If we really want to be able to control multiple devices, we'd have to refactor the UI as well.

Please @reillyeon, let me know if that looks good to you.
 
BUG=#294