Add changeOrigin option

Add changeOrigin option that changes host in request headers

Author: wclr

lib/http-proxy/common.js

@@ -74,6 +74,10 @@ common.setupOutgoing = function(outgoing, options, req, forward) {
 
   outgoing.path = common.urlJoin(targetPath, outgoingPath);
 
+  if (options.changeOrigin) {
+    outgoing.headers.host = outgoing.host;
+  }
+  
   return outgoing;
 };