Missing highlights for diffs when `git config.commentChar` is different

[ahmedelgabri]

When config.commentChar is different than # diff highlighting is not working.

I changed config.commentChar to be % instead of the default # since this conflicts with Markdown when I'm using hub CLI to open PRs etc… in specific situations.

without the parser (custom commentChar)	with the parser (custom commentChar)	with the parser (with default commentChar)

Similar to #45