Correctly document required properties

Author: jakezatecky

README.md

@@ -71,7 +71,7 @@ class Widget extends React.Component {
 | `nodes`       | array    | **Required**. Specifies the tree nodes and their children.                                    |
 | `checked`     | array    | **Required**. An array of checked node values.                                                |
 | `expanded`    | array    | **Required**. An array of expanded node values.                                               |
-| `onCheck`     | function | onCheck handler: `function(checked) {}`                                                       |
-| `onExpand`    | function | onExpand handler: `function(expanded) {}`                                                     |
+| `onCheck`     | function | **Required**. onCheck handler: `function(checked) {}`                                         |
+| `onExpand`    | function | **Required**. onExpand handler: `function(expanded) {}`                                       |
 | `name`        | string   | Optional name for the hidden `<input>` element.                                               |
 | `nameAsArray` | bool     | If true, the hidden `<input>` will encode its values as an array rather than a joined string. |

src/js/Tree.js

@@ -5,11 +5,11 @@ import nodeShape from './nodeShape';
 
 class Tree extends React.Component {
 	static propTypes = {
+		checked: React.PropTypes.arrayOf(React.PropTypes.string).isRequired,
+		expanded: React.PropTypes.arrayOf(React.PropTypes.string).isRequired,
 		onCheck: React.PropTypes.func.isRequired,
 		onExpand: React.PropTypes.func.isRequired,
 
-		checked: React.PropTypes.arrayOf(React.PropTypes.string),
-		expanded: React.PropTypes.arrayOf(React.PropTypes.string),
 		name: React.PropTypes.string,
 		nameAsArray: React.PropTypes.bool,
 		nodes: React.PropTypes.arrayOf(