add: Show how many lines does an author contribute

[kuangchanglang]

This tip comes from http://stackoverflow.com/questions/1265040/how-to-count-total-lines-changed-by-a-specific-author-in-a-git-repository Besides, git shortlog -sne shows how many commits does an author contribute

[hemanth]

Thanks for the PR, but it needs a rebase.

[kuangchanglang]

rebase done.