Issue: httprb#113

Can be used this way:

    # body will be automatically decoded when Content-Encoding is set to gzip or deflate
    HTTP.use(:auto_inflate).headers("Accept-Encoding" => "gzip").get("https://github.com").to_s

    # request body will be automatically encoded with gzip. Content-Encoding header will be automatically set to gzip
    HTTP.use(:auto_deflate).post("https://github.com", body: "Some body").to_s

    # both features can be used at the same time
    HTTP.use(:auto_inflate, :auto_deflate).headers("Accept-Encoding" => "gzip").post("https://github.com", body: "Some body")

    # deflate encoding can be used to encode body
    HTTP.use(auto_deflate: { method: :deflate }).headers("Accept-Encoding" => "gzip").post("https://github.com", body: "Some body")

Increase Metrics/MethodLength to 25
Disable Metrics/ClassLength on HTTP:Options and DummyServer::Servlet

httprb#375 (comment)

It seems `Zlib::GzipWriter.wrap` behave differently with JRuby and ruby MRI.
See jruby/jruby#4249.