Squashed 'emacs.d/git-gutter/' content from commit cd2efb5

git-subtree-dir: emacs.d/git-gutter
git-subtree-split: cd2efb54fb9ed89525ea97b9293e64e7bf6ca0d1
Merge commit '010c954deac17609ba334f40efc07512401018c3' as 'emacs.d/git-gutter'
Adding git-gutter.