frame: fix children propType

Author: nkzawa

lib/frame.js

@@ -2,7 +2,7 @@ import React, { PropTypes } from 'react';
 
 export default class Frame extends React.Component {
   static propTypes = {
-    children: PropTypes.array.isRequired,
+    children: PropTypes.any,
     component: PropTypes.string,
     duration: PropTypes.number,
     onRender: PropTypes.func