Change e-mail, and add .mailmap

Mapped my old e-mail to the new one.
git shortlog -sne also showed commits from <quinnthepigeon@gmail.com>,
which is no-longer a valid e-mail. This has also been mapped.

.stow-local-ignore

@@ -1,4 +1,5 @@
 \.git
 \.gitmodules
+\.mailmap
 LICENSE
 README\.md