Added mod+... keys to control amixer and xbacklight (note that am using sudo...

Added mod+... keys to control amixer and xbacklight (note that am using sudo here as are using acpilight (https://aur.archlinux.org/packages/acpilight/) as dropin replacement.

Also reverted compton screen-tearing fix since doesn't seem a problem for my new machine (Razer Blade 15, GTX 1060).