title: Angular Response.json() not documented
body: <p>I see Response.json() method being used a lot, and I'm using it myself, but either I'm missing something or the documentation for the Response class is incorrect.</p>
  
  <p>Example:</p>
  
  <pre><code>getCurrentTime() {
      return this._http.get('http://date.jsontest.com/')
          .map((res:Response) =&gt; res.json())
  }
  </code></pre>
  
  <p>On the Angular site at <a href="https://angular.io/docs/ts/latest/api/http/index/Response-class.html" rel="noreferrer">https://angular.io/docs/ts/latest/api/http/index/Response-class.html</a>, I don't see the method as a member of the Response class.</p>
  
  <p>If .json is <em>not</em> a member of the Response class, can someone point me in the direction of understanding how this works.</p>
  
  <p>Or if the documentation is wrong, someone please say so.</p>
  
  <p>Thanks in advance.</p>