title: Import gapi.auth2 in angular 2 typescript
body: <p>I tried to import some classes or function from Google gapi.auth2 in typescript. But below code never works even I correctly added the gapi.auth2 types in typings directory.</p>
  <pre><code>import { GoogleAuth } from 'gapi.auth2';
  </code></pre>
  <p>I always got error:</p>
  <pre><code>Error TS2307: Cannot find module 'gapi.auth2'
  </code></pre>
  <p>Shall I use some relative directory searching, such as <code>../../typings/gapi.auth2</code>?</p>
  <p>Or maybe the way I am using the gapi is totally wrong?</p>
  <p>Thanks!</p>