Merge pull request #298 from Kami/connection_keep_alive_on_1_1

If HTTP 1.1 is used and backend doesn't return 'Connection' header, expicitly  return Connection: keep-alive.

Author: indexzero

Diff for: lib/node-http-proxy/http-proxy.js

@@ -240,7 +240,14 @@ HttpProxy.prototype.proxyRequest = function (req, res, buffer) {
     //
     if (!response.headers.connection) {
       if (req.headers.connection) { response.headers.connection = req.headers.connection }
-      else { response.headers.connection = 'close' }
+      else {
+        if (req.httpVersion === '1.0') {
+          response.headers.connection = 'close'
+        }
+        else if (req.httpVersion === '1.1') {
+          response.headers.connection = 'keep-alive'
+        }
+      }
     }
 
     // Remove `Transfer-Encoding` header if client's protocol is HTTP/1.0