fix(promisify) use generic typing

script/update-license.ts

@@ -3,7 +3,7 @@
 const LICENSE = `/**
  *   Wechaty - https://github.com/chatie/wechaty
  *
- *   Copyright 2016-2017 Huan LI <zixia@zixia.net>
+ *   @copyright 2016-2017 Huan LI <zixia@zixia.net>
  *
  *   Licensed under the Apache License, Version 2.0 (the "License");
  *   you may not use this file except in compliance with the License.
@@ -134,7 +134,7 @@ async function updateLicense(file: string): Promise<void> {
 }
 
 async function glob(pattern): Promise<string[]> {
-  return promisify(globCallback)(pattern)
+  return promisify<string, string[]>(globCallback)(pattern)
 }
 
 async function main(): Promise<void> {