use latest hyper master branch to include socket buffer size fix

Cargo.toml

@@ -57,3 +57,5 @@ valgrind = ["valgrind_request"]
 
 [replace]
 "zstd-sys:1.4.10" = { path = "zstd-sys" }
+# include socket buffer size fix
+"hyper:0.12.31"  = { git = "https://github.com/hyperium/hyper.git" }

src/client/http_client.rs

@@ -163,6 +163,7 @@ impl HttpClient {
         let tlsconnector = builder.build().unwrap();
         let mut httpc = hyper::client::HttpConnector::new(1);
         httpc.set_nodelay(true); // important for h2 download performance!
+        httpc.set_recv_buf_size(Some(1024*1024)); //important for h2 download performance!
         httpc.enforce_http(false); // we want https...
         let mut https = hyper_tls::HttpsConnector::from((httpc, tlsconnector));
         https.https_only(true); // force it!