title: Redux-Form Field won't update with value of <input> inside it
body: <p>I am trying to design a type-able input component in React, which is wrapped inside a Redux-Form <code>Field</code>. But the value of the <code>Field</code> doesn't update when the value of the HTML <code>&lt;input&gt;</code> tag changes.</p>
  
  <p>The <code>Field</code> is defined as:</p>
  
  <pre><code>&lt;Field
      name="inputTextBox"
      type="text"
      component={CustomInputComponent}
  &lt;/Field&gt;
  </code></pre>
  
  <p>And the <code>CustomInputComponent</code> is defined as:</p>
  
  <pre><code>    class CustomInputComponent extends Component {
  
          constructor() {
              super();
              this.state= {
                  value: undefined
              };
  
          /* updates the state of CustomInputComponent with the current value typed inside &lt;input&gt; */
          setInputValueText = (value) =&gt; {
              this.setState({
                  ...this.state,
                  value
              })
          };
  
          render() {
              return (
                  &lt;input type="text" value={this.state.value} onInput={event =&gt; this.setInputValueText(event.target.value)} /&gt;
              )
  
      }
  </code></pre>
  
  <p>Whenever the <code>&lt;input&gt;</code> tag is typed into, the state of the <code>CustomInputComponent</code> changes successfully, but the value of the <code>Field</code> above that contains <code>CustomInputComponent</code> doesn't change. I am trying to access the value of the <code>Field</code> through:</p>
  
  <pre><code>const selector = formValueSelector('myForm')
  let currentInput = selector(state, 'inputTextBox')
  </code></pre>
  
  <p>I want <code>currentInput</code> to contain the current value typed inside <code>input</code>. What could I be missing?</p>