Only show recommended tab for opt-in users (bug 1097332)

ah, gotcha. so if that's the case instead of calling `z.body.removeClass('show-recommendations')` _before_ the user logs out, can you change [the line in the `reload_chrome` event listener](https://github.com/mozilla/fireplace/blob/master/src/media/js/main.js#L207) to run `z.body.toggleClass('show-recommendations')` instead?

it'd be nice to keep things in the same place. all I'm sayin', mayne.