** 무엇을 변경하셨나요? **

[jooseung]

React.PropTypes 사용을 더욱 좋게 변경하였습니다.

** 왜 수정하셨나요? **
더 간단하고 가독성이 좋습니다.

** 테스트 계획 **

** 이슈번호 **
#14

Jsing

Signed-off-by: Jsing gkswntmd@gmail.com

Before submitting a pull request, please make sure the following is done:

1. Fork the repository and create your branch from master.
2. If you've added code that should be tested, add tests!
3. If you've changed APIs, update the documentation.
4. Ensure the test suite passes (npm test).
5. Make sure your code lints (npm run lint).
6. Format your code with prettier (npm run prettier).
7. Run the Flow typechecks (npm run flow).
8. If you added or removed any tests, run ./scripts/fiber/record-tests before submitting the pull request, and commit the resulting changes.
9. If you haven't already, complete the CLA.