Transform propTypes and defaultProps

eg:

```js
Appear.defaultProps = {
  transitionDuration: 300
};

Appear.propTypes = {
  children: PropTypes.node,
  fragment: PropTypes.object,
  route: PropTypes.object,
  style: PropTypes.object,
  transitionDuration: PropTypes.number
};
```

and

```js
class Appear extends Component {
  static propTypes = {}
}
```