message: refactor BorderBox
diff: -import {withSystemProps} from './system-props'
  +import styled from 'styled-components'
  import Box from './Box'
  +import theme from './theme'
  +import {BORDER} from './constants'
  -const BorderBox = withSystemProps(
  - {
  - is: Box,
  - border: 1,
  +const BorderBox = styled(Box)`
  + ${BORDER};
  +`
  +
  +BorderBox.defaultProps = {
  + theme,
  + border: '1px solid',
  borderColor: 'gray.2',
  borderRadius: 1
  - },
  - ['boxShadow']
  -)
  +}
  +// spread prop types here
  BorderBox.propTypes = {
  - ...Box.propTypes
  + ...Box.propTypes,
  + ...BORDER.propTypes
  }
  export default BorderBox
  