Ungzipping gzipped response from prerender service produces corrupted unicode strings

[ilyazolotarov]

This is where bad things happens - if chunk contains only part of unicode character then implicit Buffer.toString() produces corrupted string.

The fix will be to keep an array of chunks and then invoking Buffer.concat(chunks).toString() at the end.

Simple repro with hotfix

[ilyazolotarov]

Just noticed that prerender.plainResponse can also have this bug. Not sure if chunk is Buffer or String in this case.