Fix Thenable compile error

Author: dbaeumer

jsonrpc/src/main.ts

@@ -2,7 +2,7 @@
  * Copyright (c) Microsoft Corporation. All rights reserved.
  * Licensed under the MIT License. See License.txt in the project root for license information.
  * ------------------------------------------------------------------------------------------ */
-/// <reference path="./thenable.d.ts" />
+/// <reference path="../typings/thenable.d.ts" />
 'use strict';
 
 import * as Is from './is';