Pass children down to Checkboard
I'd like to use checkboard as a background for a button.

e.g.

```
<Checkboard>
        <button/>
</Checkboard>
```

This would be very simple if https://github.com/casesandberg/react-color/blob/master/src/components/common/Checkboard.js passed down the children prop to the div

Would that be ok? 