title: how can start and stop an interval observable in RXJS?
body: <p>I have a very simple timeInterval observable and I want to start/stop transmission without disconnecting subscribers (which should sit and wait regardless of observable status). Is possible, and if so how?</p>
  
  <pre><code>var source = Rx.Observable
    .interval(500)
    .timeInterval()
    .map(function (x) { return x.value + ':' + x.interval; })
    .take(10);
  
    var subscription = source.subscribe(
    function (x) {
       $("#result").append('Next: ' + x + ' ');
    },
    function (err) {
      $("#result").append('Error: ' + err);
    },
    function () {
      $("#result").append('Completed');
    });
  </code></pre>
  
  <p>general comment: most of the examples ive seen show how to define observables and subscribers. how do i affect the behavior of existing objects?</p>