배포 환경 별 requirements.txt 분리

# 로컬
pip install -r requirements/dev.txt

# 프로덕션 서버
pip install -r requirements/prod.txt

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common.txt보단 base.txt가 더 적절한 네이밍인 거 같다.
그렇게 수정하자

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https://stackoverflow.com/questions/17803829/how-to-customize-a-requirements-txt-for-multiple-environments