Fix typo in README.md

[nephtyws]

Includes the smallest fix that change mananage to manage

[coveralls]

Pull Request Test Coverage Report for Build 51

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.443%

---

Totals
Change from base Build 42:	0.0%
Covered Lines:	57
Relevant Lines:	61

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💛 - Coveralls

[iamchanu]

참고로 이번처럼 코드 수정이 없을 때에는, 커밋 메세지에 [ci skip] 을 붙이면 Travis CI 가 불필요하게 실행되는 것을 막을 수 있습니다.
...그런데 CI 빌드가 실패했네요 ㅠㅠ
pytest 버전의 문제인 것 같은데, 수정해 보겠습니다.