Fix README for latest React changes

Author: danez

README.md

@@ -119,42 +119,41 @@ For example, while the `propTypesHandler` expects the prop types definition to b
 For the following component
 
 ```js
-var React = require('react');
+import React, { Component } from 'react';
+import PropTypes from 'prop-types';
 
 /**
  * General component description.
  */
-var Component = React.createClass({
-  propTypes: {
-    /**
-     * Description of prop "foo".
-     */
-    foo: React.PropTypes.number,
-    /**
-     * Description of prop "bar" (a custom validation function).
-     */
-    bar: function(props, propName, componentName) {
-      // ...
-    },
-    baz: React.PropTypes.oneOfType([
-      React.PropTypes.number,
-      React.PropTypes.string
-    ]),
-  },
-
-  getDefaultProps: function() {
-    return {
-      foo: 42,
-      bar: 21
-    };
-  },
-
+class MyComponent extends Component {
   render: function() {
     // ...
   }
-});
+}
 
-module.exports = Component;
+MyComponent.propTypes = {
+  /**
+   * Description of prop "foo".
+   */
+  foo: PropTypes.number,
+  /**
+   * Description of prop "bar" (a custom validation function).
+   */
+  bar: function(props, propName, componentName) {
+    // ...
+  },
+  baz: PropTypes.oneOfType([
+    PropTypes.number,
+    PropTypes.string
+  ]),
+};
+
+MyComponent.defaultProps = {
+  foo: 42,
+  bar: 21
+};
+
+export default Component;
 ```
 
 we are getting this output: