`createElement` and `cloneElement`

There is currently no support for using `createElement` and `cloneElement` with the `styleName` attribute (as far as I've tried), which at times can be a bit painful.

```jsx
render() {
const element = ordered ? 'ol' : 'ul';

return React.createElement(
element,
{
styleName: 'example-style', // <-- This
},
);
}
```

-->

```
Warning: React does not recognize the `styleName` prop on a DOM element. If you intentionally want it to appear in the DOM as a custom attribute, spell it as lowercase `stylename` instead. If you accidentally passed it from a parent component, remove it from the DOM element.
```

I haven't read through the source code but t would assume it is a transform thing, where the `styleName` prop is not read as it's not a JSX prop but rather a passed in as an object. JSX gets transformed into `createElement`s so I would've guessed that this would work automatically but I guess not, unless I'm doing something wrong here.

Wondering if there's any ability for future support?