title: Cannot find external module 'angular2/angular2' - Angular2 w/ Typescript
body: <p>I am going through the step by step tutorial on angular.io (Angular 2). I am using typescript. I get the following error when trying to compile:</p>
  
  <p><code>Cannot find external module 'angular2/angular2'</code></p>
  
  <p>using the watch command.</p>
  
  <p><strong>main.ts</strong></p>
  
  <pre><code>import {Component, View, bootstrap} from 'angular2/angular2';
  
  @Component({
    selector: 'my-app'
  })
  
  @View({
    template: '&lt;h1&gt;My first Angular 2 App&lt;/h1&gt;'
  })
  
  class AppComponent {
  }
  
  bootstrap(AppComponent);
  </code></pre>
  
  <p><strong>index.html</strong></p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
    &lt;head&gt;
      &lt;script src="https://jspm.io/system@0.16.js"&gt;&lt;/script&gt;
      &lt;script src="https://code.angularjs.org/2.0.0-alpha.23/angular2.dev.js"&gt;&lt;/script&gt;
    &lt;/head&gt;
    &lt;body&gt;
  
      &lt;my-app&gt;&lt;/my-app&gt;
  
      &lt;script&gt;
        System.import('main');    
      &lt;/script&gt;
  
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p><strong>Q</strong> Why is this error occuring?</p>