Fix incorrect caching headers if gzip is enabled by etag is not
Fix incorrect caching headers if gzip is enabled by etag is not

Vary: Accept-Encoding is required if sending back gzipped data, or caching layers may cache a gzipped response and serve it to users without Accept-Encoding: gzip.  As far as I know, it has nothing to do with ETags.
ForbesLindesay/prepare-response,ForbesLindesay/prepare-response