message: docs(tutorial): fix an example
diff: @@ -132,10 +132,10 @@ class MyComponent extends ObservableComponent {
  }
  componentDidMount() {
  this.messages = messages
  - // Let accumulate our messages in an array
  + // Accumulate our messages in an array
  .scan((messages, message) => [message].concat(messages), [])
  // And render whenever we get a new message
  - .forEach(messages => this.setState({messages: messages}));
  + .subscribe(messages => this.setState({messages: messages}));
  }
  componentWillUnmount() {
  this.messages.unsubscribe();
  