revert Grit::Index#commit default value for parents arg
revert Grit::Index#commit default value for parents arg

patientslikeme/grit,isabanin/grit,brynary/grit,HrishikeshSingh/testmodulerepo,redronin/grit,kevinsawicki/grit,kevinsawicki/grit,brynary/grit,isabanin/grit,github/grit,thommay/grit,thommay/grit,gitlabhq/grit,mojombo/grit,rgroux/grit,gitcafe-dev/grit,HrishikeshSingh/testmodulerepo,gitcafe-dev/grit,gitlabhq/grit,rgroux/grit,flycutter/grit,abicky/grit,renatoramiro/grit,flycutter/grit