Add git-gutter+, git-gutter-fringe+

git-gutter+ adds hunk staging and committing (plus many bugfixes) to [git-gutter](https://github.com/syohex/emacs-git-gutter).
Hopefully, both projects will be merged someday.

https://github.com/nonsequitur/git-gutter-plus
https://github.com/nonsequitur/git-gutter-fringe-plus

Thanks for MELPA :)