message: docs(tutorial): Log target values and not the events
  We want to log the input values and not the keypress events.
diff: @@ -52,27 +52,33 @@ var input = Rx.Observable.fromEvent(document.querySelector('input'), 'input');
  // Filter out target values less than 3 characters long
  input.filter(event => event.target.value.length > 2)
  + .map(event => event.target.value)
  .subscribe(value => console.log(value)); // "hel"
  // Delay the events
  input.delay(200)
  + .map(event => event.target.value)
  .subscribe(value => console.log(value)); // "h" -200ms-> "e" -200ms-> "l" ...
  // Only let through an event every 200 ms
  input.throttleTime(200)
  + .map(event => event.target.value)
  .subscribe(value => console.log(value)); // "h" -200ms-> "w"
  // Let through latest event after 200 ms
  input.debounceTime(200)
  + .map(event => event.target.value)
  .subscribe(value => console.log(value)); // "o" -200ms-> "d"
  // Stop the stream of events after 3 events
  input.take(3)
  + .map(event => event.target.value)
  .subscribe(value => console.log(value)); // "hel"
  // Passes through events until other observable triggers an event
  var stopStream = Rx.Observable.fromEvent(document.querySelector('button'), 'click');
  input.takeUntil(stopStream)
  + .map(event => event.target.value)
  .subscribe(value => console.log(value)); // "hello" (click)
  ```
  