Clarify help message and fix grammar ("a projects commits") along the way
Clarify help message and fix grammar ("a projects commits") along the way

Signed-off-by: Chris Wanstrath <711c73f64afdce07b7e38039a96d2224209e9a6c@ozmm.org>
bfg-repo-cleaner-demos/github-gem-after-bfg