= httpx: fix Deflate reporting wrong number of remaining bytes, fixes #583

Before Deflate.decompress always assumed `inflater.finished()` was already
working on the last 1024-Byte chunk of input data when in fact it could be
anywhere else. The test-case was pathological because of its compressed size
being just a few bytes more than the internal buffer of 1024.
Merge pull request #584 from jrudolph/i/583/gzip-problem

= httpx: fix Deflate reporting wrong number of remaining bytes, fixes #583