Up-to-date React.Children

Make sure we actually include `.count`

Author: Mouad Debbar

src/browser/ui/React.js

@@ -45,6 +45,7 @@ var React = {
   Children: {
     map: ReactChildren.map,
     forEach: ReactChildren.forEach,
+    count: ReactChildren.count,
     only: onlyChild
   },
   DOM: ReactDOM,