fix Touchables inspector

Summary:
Fix TouchableWithoutFeedback throw error when touchables inspector is shown in react@15.4.0:
`Attempted to assign to readonly property`
![image](https://cloud.githubusercontent.com/assets/7693239/20824463/14f7bfc8-b898-11e6-9bc3-50434492ee40.png)

Convert children into an array by using React.Children.toArray.
Closes #11262

Differential Revision: D4329147

fbshipit-source-id: 38c9f78b5a81964efccacc7a08b66dda7acb7dc5

Libraries/Components/Touchable/TouchableWithoutFeedback.js

@@ -157,9 +157,7 @@ const TouchableWithoutFeedback = React.createClass({
         ((child._owner && child._owner.getName && child._owner.getName()) || '<unknown>')
     );
     if (Touchable.TOUCH_TARGET_DEBUG && child.type && child.type.displayName === 'View') {
-      if (!Array.isArray(children)) {
-        children = [children];
-      }
+      children = React.Children.toArray(children);
       children.push(Touchable.renderDebugView({color: 'red', hitSlop: this.props.hitSlop}));
     }
     const style = (Touchable.TOUCH_TARGET_DEBUG && child.type && child.type.displayName === 'Text') ?