UI bug fixes.

Ran grunt test.

Fixes in this pull request
- Change the title of the extension popup from "uProxy polymer UI" to "uProxy" 
- Instead of closing/reopening the popup each time the popup URL changes, update the URL of the popup. (This prevents a weird flash where the "install app" popup opens, the app connects, and the popup immediately closes.)
- vulcanize Chrome extension Polymer code.