Because we're setting far-future `Cache-Control` `max-age`s on the resources defined in the appcache manifest, we need to add querystring parameters to properly cachebust the resources listed in the appcache manifest. The cachebusting-querystring parameter should be a hash of the resource's contents, so we don't accidentally invalidate a resource when it actually hasn't changed.

https://github.com/mozilla/darjeeling/commit/d2ec568 Wooooooo! This is awesome!

Reverted: https://github.com/mozilla/darjeeling/commit/b23d925 We don't need this anymore. As long as we never set `Cache-Control`/`Expires` headers and always stick to `ETag`s, we don't need to do cachebusting. And there's no perf hit incurred anyway.