Add git_uncommitted/unstaged_files()
Add git_uncommitted/unstaged_files()

While we have used a line count for a while, we haven't ever used a file
count for the same stats. I don't know if the default theme will end up
using this, but some other theme probably will.

laurentbardin/liquidprompt,milouse/liquidprompt,jaesivsm/liquidprompt,nojhan/liquidprompt,pkkolos/liquidprompt