Update AUTHORS file

Using:
    git log --format="%aN" | sort | uniq -c \
        | sort -rn | awk '$1 >=15 {$1=""; print $0}' \
        | cut -d" " -f2- > AUTHORS

AUTHORS

@@ -1,21 +1,23 @@
 David Winterbottom
 Maik Hoepfel
+Michael van Tellingen
 Sebastian Vetter
 Jon Price
-Andrew Ingram
 Markus Bertheau
+Andrew Ingram
 Asia Biega
 Xavier Ordoquy
 Oliver Randell
 Izidor Matušov
 Eleni Lixourioti
 Tomasz Rybarczyk
 Andy Sellick
+John Parton
 Kura
-Michael van Tellingen
 Pavel Vavruska
 Patryk Zawadzki
 Jonathan Moss
+Alexander Gaevsky
 andysellick
 Paweł Kowalski
 Dawid Lorenz