Fix double filters load

filters.js has been loading twice in browsers greater than IE8 (which includes all Firefox, Chrome, Safari). This can cause unexpected behavior since the code executes at load time (twice), and also adds an unnecessary GET. This PR resolves that by removing filters.js from the "greater than IE8" block and naming that "listings-not-ie8".

This PR also includes PR 99: https://github.com/mozilla/lumbergh/pull/99