Req adapter: assess streaming decompression status

[mwhitworth]

reverse_proxy_plug/lib/reverse_proxy_plug/http_client/adapters/req.ex

Line 71 in 420e97a

# Versions >= 0.4.0 and < 0.4.12 specify a compressed body automatically, but

contains a workaround that may not apply to 0.5.0 and above