Fix propTypes error that caused JS console error.

See also formio#449
and      formio#425

src/components/Form.jsx

@@ -13,11 +13,11 @@ export default class Form extends Component {
  form: PropTypes.object,
  submission: PropTypes.object,
  options: PropTypes.shape({
- readOnly: PropTypes.boolean,
- noAlerts: PropTypes.boolean,
+ readOnly: PropTypes.bool,
+ noAlerts: PropTypes.bool,
  i18n: PropTypes.object,
  template: PropTypes.string,
- saveDraft: PropTypes.boolean,
+ saveDraft: PropTypes.bool,
  }),
  onPrevPage: PropTypes.func,
  onNextPage: PropTypes.func,