Remove unused imports in bears

[jayvdb]

Remove the following unused imports, to help prepare for coala/coala#3066

./bears/python/MypyBear.py:7: 'coalib.results.RESULT_SEVERITY.RESULT_SEVERITY' imported but unused
./bears/python/MypyBear.py:8: 'coalib.results.Result.Result' imported but unused
./bears/python/YapfBear.py:1: 'sys' imported but unused
./bears/vcs/git/GitCommitBear.py:11: 'coalib.results.RESULT_SEVERITY.RESULT_SEVERITY' imported but unused
./bears/natural_language/LanguageToolBear.py:29: 'language_check.correct' imported but unused
./bears/natural_language/LanguageToolBear.py:29: 'language_check.LanguageTool' imported but unused

[iamprakashom]

I am working on this.

[jayvdb]

Could you please follow http://coala.io/newcomer (come onto gitter...)

[iamprakashom]

I am on it 😄
joined gitter too.