_getClass () {
    return 'sc-button'
  }
Acts like a link if `url` is provided. Sends an action if `action` is
provided. Uses default behaviour if none of both provided.

Examples:

```
$$(Button, { style: 'primary', action: 'createVersion' }, 'Create Version')
$$(Button, { style: 'primary', size: 'large', url: '/login' }, 'Login')
$$(Button, { style: 'primary', size: 'large' }, 'Request login link')
$$(Button, { style: 'default', size: 'large', action: 'closeModal' }, 'Cancel')
$$(Button, { style: 'default', size: 'small', action: 'replaceImage' }, 'Replace Image')
```