#!++: Reverse mouse wheel

swap 4 and 5 using the following command. It may require restart x.

xmodmap -e "pointer = 1 2 3 5 4"

above is deprecated:- does not work for Chrome 49

xinput set-prop 10 "Evdev Scrolling Distance" -1 1 1
xmodmap -e "pointer = 1 2 3 4 5"