Update CONTRIBUTORS.txt

CONTRIBUTORS.txt

@@ -171,3 +171,4 @@ John Whitlock, 2014/08/19
 Konstantinos Koukopoulos, 2014/08/24
 Andrea Rabbaglietti, 2014/10/02
 Joe Jevnik, 2014/10/22
+Nathan Van Gheem, 2014/10/28