Use ES6 in Language Tooling doc

docs/09.1-language-tooling.md

@@ -37,28 +37,23 @@ Example output:
 
 ```
 $ cat test.js
-var HelloMessage = React.createClass({
-  render: function() {
-    return <div>Hello {this.props.name}</div>;
-  }
-});
+function HelloMessage(props) {
+  return <div>Hello {props.name}</div>;
+}
 
 ReactDOM.render(<HelloMessage name="John" />, mountNode);
+
 $ babel test.js
 "use strict";
 
-var HelloMessage = React.createClass({
-  displayName: "HelloMessage",
-
-  render: function render() {
-    return React.createElement(
-      "div",
-      null,
-      "Hello ",
-      this.props.name
-    );
-  }
-});
+function HelloMessage(props) {
+  return React.createElement(
+    "div",
+    null,
+    "Hello ",
+    props.name
+  );
+}
 
 ReactDOM.render(React.createElement(HelloMessage, { name: "John" }), mountNode);
 ```