add support for harmony features of jsx

This pull request adds support for the harmony features of react-tools.

I was a bit too early though as this is only enabled in master of react (see https://github.com/facebook/react/blob/master/main.js), so maybe this pull request can wait until 0.10 is released.

Note: You can use the harmony features already, because the harmony features are implemented in react 0.9. You only need the master of main.js