[fix] fix #738

Author: jcrugzz

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

@@ -150,7 +150,7 @@ common.urlJoin = function() {
   retSegs = [
     args.filter(function filter(a) {
       return !!a;
-    }).join('/').replace(/\/+/g, '/')
+    }).join('/').replace(/\/+/g, '/').replace(/:\//g, '://')
   ];
 
   // Only join the query string if it exists so we don't have trailing a '?'