title: redux-form: Field value does not reflect state change
body: <p>I have started using redux-form just recently and found an issue which I am not sure how to solve and although I suppose it must be something really easy I am not able to find answer anywhere. </p>
  
  <p>Issue: Value of the Field (redux-form Field) is not updated when state changes.</p>
  
  <p>Example*:</p>
  
  <pre><code> const SimpleForm = (props) =&gt; {
      return (
          &lt;Form onSubmit={props.handleSubmit}&gt;            
              &lt;Field value={props.amount} onChange={props.amountChanged}
                  name="amount" component={renderField} /&gt;
  
              &lt;input value={props.amount} type="text" onChange={props.amountChanged} /&gt;
          &lt;/Form&gt;
      );
  };
  
  const renderField = (field) =&gt; (
      &lt;div className="input-row"&gt;
          &lt;input {...field.input} type="text" /&gt;
          {field.meta.touched &amp;&amp; field.meta.error &amp;&amp; &lt;span className="error"&gt;{field.meta.error}&lt;/span&gt;}
      &lt;/div&gt;
  )
  
  export default reduxForm({ form: 'SimpleForm' })(SimpleForm);
  </code></pre>
  
  <p><strong>Expected Result:</strong></p>
  
  <ul>
  <li><p>initial value in both inputs is same (and equals to props.amount)</p></li>
  <li><p>when I change value in one of the inputs the second input is updated with a new value</p></li>
  </ul>
  
  <p><strong>Actual Result:</strong></p>
  
  <ul>
  <li><p>initial value in input 'wrapped' into redux-form field is not populated</p></li>
  <li><p>when I change value in 'redux-form input' -> 'normal input' is updated BUT 
      when I change value in 'normal input' -> 'redux form input' is not updated</p></li>
  </ul>
  
  <p><strong>Question:</strong></p>
  
  <ul>
  <li>does anybody happen to know why redux-form input is not updated when state value is changed?</li>
  </ul>
  
  <p>*Please note that: onChange just basically triggers action which is handled by reducers and state is updated with new amount; 'renderField' function is taken from <a href="http://redux-form.com/6.7.0/docs/api/Field.md/#usage" rel="nofollow noreferrer">redux-form component usage page</a> and SimpleForm is used in some really basic 'statefull' container</p>