changeOrigin option: set the host header to the proxy destination

lib/node-http-proxy/http-proxy.js

@@ -194,7 +194,9 @@ HttpProxy.prototype.proxyRequest = function (req, res, buffer) {
   outgoing.method  = req.method;
   outgoing.path    = req.url;
   outgoing.headers = req.headers;
-  outgoing.headers.host = this.target.host + (this.target.port == 80 ? '' : ':' + this.target.port)
+
+  if(this.changeOrigin)
+    outgoing.headers.host = this.target.host + (this.target.port == 80 ? '' : ':' + this.target.port)
   //
   // Open new HTTP request to internal resource with will act 
   // as a reverse proxy pass