Add .coverage to .gitignore
Add .coverage to .gitignore

This file is generated by the 'coverage' tool.

Also, add / to beginning of entries that should only
be ignored in the root of the repo.

bygloam/yapf,thurday/yapf,ambv/yapf,lucius-feng/yapf,sbc100/yapf,dmoliveira/yapf,google/yapf,abduld/yapf,sbc100/yapf,nikolamilosevic86/yapf,google/yapf,hayd/yapf,elviswf/yapf,jamesblunt/yapf,wklken/yapf