Always send body whole and don't use transfer encoding

Without doing this, body size would be unknown at the time of sending, causing awc to use transfer encoding which is probably unexpected in most cases.
This change makes behavior more obvious.

http-proxy/src/main.rs

@@ -7,7 +7,7 @@ use url::Url;
 
 fn forward(
     req: HttpRequest,
-    payload: web::Payload,
+    body: web::Bytes,
     url: web::Data<Url>,
     client: web::Data<Client>,
 ) -> impl Future<Item = HttpResponse, Error = Error> {
@@ -25,14 +25,16 @@ fn forward(
     };
 
     forwarded_req
-        .send_stream(payload)
+        .send_body(body)
         .map_err(Error::from)
         .map(|res| {
             let mut client_resp = HttpResponse::build(res.status());
+            // Remove `Connection` as per
+            // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Connection#Directives
             for (header_name, header_value) in res
                 .headers()
                 .iter()
-                .filter(|(h, _)| *h != "connection" && *h != "content-length")
+                .filter(|(h, _)| *h != "connection")
             {
                 client_resp.header(header_name.clone(), header_value.clone());
             }