Add mgol's name to AUTHORS, add .mailmap

In this way mgol's past contribution is mapped correctly.
2017-11-22 10:46:11 +01:00 · 2017-11-22 10:46:11 +01:00 · a9135f5c35
--- a/.mailmap
+++ b/.mailmap
@ -0,0 +1 @@
 Michał Gołębiowski-Owczarek <m.goleb@gmail.com>
--- a/1
+++ b/1
@ -16,6 +16,7 @@ Jonas Jenwald <jonas.jenwald@gmail.com>
 Julian Viereck
 Justin D'Arcangelo <justindarc@gmail.com>
 Kalervo Kujala
 Michał Gołębiowski-Owczarek <m.goleb@gmail.com>
 Ophir Lojkine <@lovasoa>
 Rob Wu <rob@robwu.nl>
 Shaon Barman <shaon.barman@gmail.com>
		`@ -0,0 +1 @@`
							`Michał Gołębiowski-Owczarek <m.goleb@gmail.com>`