Add .mailmap file

Use .mailmap to fix author names and emails in git log / git shortlog -e.

Fixes #103.

.mailmap

+Aaron Griffin <aaron@archlinux.org> <aaronmgriffin@gmail.com>
+Chandan Singh <cks071g2@gmail.com> chandan <cks071g2@gmail.com>
+Charles Vejnar <ce@vejnar.org> Charles <ce@vejnar.org>
+Christopher Brannon <cmbrannon79@gmail.com> <cmbrannon@cox.net>
+David Runge <dvzrv@archlinux.org> <dave@sleepmap.de>
+Eli Schwartz <eschwartz@archlinux.org> Eli Schwartz via arch-releng <arch-releng@archlinux.org>
+Francois Dupoux <fdupoux@users.sourceforge.net> fdupoux <fdupoux@users.sourceforge.net>
+Gerardo Exequiel Pozzi <vmlinuz386@gmail.com> <vmlinuz386@yahoo.com.ar>
+James Sitegen <jamesm.sitegen@gmail.com> jamesm-sitegen <jamesm.sitegen@gmail.com>
+Keshav Amburay <the.ridikulus.rat@gmail.com> Keshav P R <the.ridikulus.rat@gmail.com>
+Martin Damian Fernandez <martin.damian.fernandez@gmail.com> martindamianfernandez <martin.damian.fernandez@gmail.com>
+Michael Vorburger <mike@vorburger.ch> Michael Vorburger.ch <mike@vorburger.ch>
+Sean Enck <enckse@voidedtech.com> Sean Enck via arch-releng <arch-releng@archlinux.org>
+Simo Leone <simo@archlinux.org> <leone.simo@gmail.com>
+Sven-Hendrik Haase <svenstaro@gmail.com> <sh@lutzhaase.com>
+Yu Li-Yu <afg984@gmail.com> Li-Yu Yu via arch-releng <arch-releng@archlinux.org>