[git] 마지막 commit commet 수정

$ git commit --amend

http://git-scm.com/book/ko/Git-%EB%8F%84%EA%B5%AC-%ED%9E%88%EC%8A%A4%ED%86%A0%EB%A6%AC-%EB%8B%A8%EC%9E%A5%ED%95%98%EA%B8%B0