Dlc 17 - Listings UI [IN-PROGRESS]

@Saityi make a pull request next time and tag me. Don't be shy :)
Whoops! Alas, the status code causes the redirect to render as a successful page that says 'You are being redirected' (via [this](https://stackoverflow.com/questions/4310913/ruby-on-rails-how-to-get-rid-of-you-are-being-redirected-page)) but never actually redirects. The browser sees 200 and says, 'oh, hey, they want to have a nice page that tells them they're being redirected'. Haha. Apparently that is actually a bad idea. :(

The listings controller destroy action just does `redirect_to current_admin` now, and the test ensures that the destroy action renders the admin show action. I think the other makes more sense, but it's broken.