title: RxJS emit array items over time?
body: <p>I'm trying to emit simple array values one after another with 500ms in between:</p>
  
  <pre><code>var a = Rx.Observable.from([1,2,3]);
  a.interval(500).subscribe(function(b) { console.log(b); });
  </code></pre>
  
  <p>However, this throws an exception:</p>
  
  <pre><code>Uncaught TypeError: a.interval is not a function.
  </code></pre>