title: Repeat request (Angular2 - http.get) n seconds after finished
body: <p>I played around with angular2 and got stuck after a while.</p>
  
  <p>Using <code>http.get</code> works fine for a single request, but I want to poll live-data every 4 seconds, after tinkering for quite a while and reading a lot of reactivex stuff i ended up with:</p>
  
  <pre><code>Observable.timer(0,4000)
    .flatMap(
      () =&gt; this._http.get(this._url)
         .share()
         .map(this.extractData)
         .catch(this.handleError)
    )
    .share(); 
  </code></pre>
  
  <p>Is there a <em>simple</em> way to start a (4 second) interval after the <code>http.get</code>-observable has emitted the result of the request? (Or will I end up in <em>observable-hell</em>?)</p>
  
  <p>Timeline i want:</p>
  
  <pre><code>Time(s): 0 - - - - - 1 - - - - - 2 - - - - - 3 - - - - - 4 - - - - - 5 - - - - - 6
  Action:  Request - - Response - - - - - - - - - - - - - - - - - - - -Request-... 
  Wait:                | wait for 4 seconds -------------------------&gt; |
  </code></pre>