message: simplify Button private API
diff: @@ -13,10 +13,7 @@ function fontSize({size = '14px', ...props}) {
  }
  }
  -const Button = styled.button.attrs(props => ({
  - disabled: props.disabled,
  - onClick: props.disabled ? undefined : props.onClick
  -}))`
  +const Button = styled.button`
  ${props => (props.theme ? getButtonStyles(props.theme) : '')};
  ${fontSize};
  ${COMMON};
  