modify require usage in accordance to the new style mentioned in addon sdk documentation
adding "private-browsing"=false in package.json
adding "permissions": {"private-browsing": false} in package.json to ready for new private browsing API: https://blog.mozilla.org/addons/2013/02/26/per-window-private-browsing-and-the-add-on-sdk/. I'd have loved to have supported showing QR on private windows too. But, due to https://bugzilla.mozilla.org/show_bug.cgi?id=816257, panel and private window won't go hand-in-hand :(