Per-file cache busting for skin js and media URLs with no web-server config.
Browsers and CDNs hold onto stale skin CSS, JS and media URLs across deploys, leading to white-screen layouts and broken-looking pages until the cache expires.
Cache Buster post-processes rendered HTML and appends a per-file ?v=<mtime> to every same-origin /skin/ /js/ and /media/ asset URL so a changed file is fetched fresh, with no nginx or apache rewrite rules required.
