Pass through refs and props to all layers of AsyncCreatable.

This enables users of AsyncCreatable to hook the Select which is
created and/or access it as a ref.

Previously there was no way to get at the underlying Select if
you used AsyncCreatable.

src/AsyncCreatable.js

@@ -7,19 +7,42 @@ const AsyncCreatable = React.createClass({
 	render () {
 		return (
 			<Select.Async {...this.props}>
-				{(asyncProps) => (
-					<Select.Creatable {...this.props}>
-						{(creatableProps) => (
-							<Select
-								{...asyncProps}
-								{...creatableProps}
-							/>
-						)}
+				{({ref, ...asyncProps}) => {
+					const asyncRef = ref
+					return <Select.Creatable {...asyncProps} >
+						{({ref, ...creatableProps}) => {
+							const creatableRef = ref
+							return this.props.children({
+								...creatableProps,
+								ref: (select) => {
+									creatableRef(select)
+									asyncRef(select)
+									this.select = select
+								}
+							})
+						}}
 					</Select.Creatable>
-				)}
+				}}
 			</Select.Async>
 		);
 	}
 });
 
+function defaultChildren (props) {
+	return (
+		<Select {...props} />
+	);
+};
+
+const propTypes = {
+	children: React.PropTypes.func.isRequired, // Child function responsible for creating the inner Select component; (props: Object): PropTypes.element
+}
+
+const defaultProps = {
+	children: defaultChildren,
+}
+
+Async.propTypes = propTypes;
+Async.defaultProps = defaultProps;
+
 module.exports = AsyncCreatable;