title: React ES6 parent child components state issue
body: <p>I am new to react and trying to build a simple ToDo app based off of the react-starter-kit. I am using ES6 classes and unable to find a way to update parent state from a child component.</p>
  
  <p>Here is the code:  </p>
  
  <pre><code>import React, { PropTypes, Component } from 'react';
  import withStyles from '../../decorators/withStyles';
  import styles from './ToDoPage.less';
  
  
  @withStyles(styles)
  class ToDoPage extends Component {
  
    static contextTypes = {
      onSetTitle: PropTypes.func.isRequired
    };
  
    constructor() {
      super();
      this.state = {
        items: ['Item1', 'Item2'],
        value: ''
      };
    }
  
    updateValue(newValue) {
      //this.state is null here
      this.setState({
        value: newValue 
      });
    }
  
    clickHandler() {
      console.log('AddToDo state:', this.state)
      if (this.state.value &amp;&amp; this.state.items) { //this.state is null here
        this.setState({
          items: this.state.items.push(this.state.value)
        });
      }
    }
  
    render() {
      let title = 'To Do List';
      this.context.onSetTitle(title);
      return (
        &lt;div className="ToDoPage"&gt;
         &lt;div className="ToDoPage-container"&gt;
          &lt;h1&gt;{title}&lt;/h1&gt;
            &lt;AddToDoTextBox handleUpdate={this.updateValue}/&gt;
            &lt;AddToDoButton handleClick={this.clickHandler}/&gt;
            &lt;div className = "todo-items"&gt;
             &lt;br/&gt;
             &lt;div&gt;({this.state.items.length}) items found.&lt;/div&gt;
             &lt;ToDoList items = {this.state.items}/&gt;
            &lt;/div&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      );
    };
  }
  
  class ToDoList extends Component {
    static propTypes = {
      items: PropTypes.array.isRequired
    };
  
    render() {
      console.log(this.props.items);
      return (
              &lt;ul&gt;
              {this.props.items.map(function(item) {
               return &lt;li key={item}&gt;{item}&lt;/li&gt;
              }) }
              &lt;/ul&gt;); 
    };
  };
  
  class AddToDoButton extends Component {
    static propTypes: {
      clickHandler: React.PropTypes.func 
    }
  
    constructor() {
      super(); 
    }
  
    render() { 
      return (&lt;button 
              className="btn btn-primary" 
              onClick={this.props.handleClick.bind(this)}&gt;Add ToDo&lt;/button&gt;); 
    };
  }
  
  class AddToDoTextBox extends Component {
    static propTypes: {
      handleUpdate: React.PropTypes.func
    }
  
    constructor() {
      super();
      this.state = {
        value: '' 
      };
      this.handleChange = this.handleChange.bind(this);
    }
  
    handleChange(e) {
      this.setState({value: e.target.value}); 
      this.props.handleUpdate.call(this, e.target.value);
    }
  
    render() {
      return &lt;input type="text" placeholder="Enter todo item here" size="50" onChange={this.handleChange}/&gt; 
    };
  }
  export default ToDoPage;
  </code></pre>
  
  <p>I want to access ToDoPage's state from updateValue() and clickHandler() functions but this.state is null as I binding to the child components they are being called from (i.e AddToDoButton and AddToDoTextBox). How can I access/update ToDoPage's state from clickHandler() or updateValue()?</p>