i3lock improves slock by making it fork() and therefore combinable with
commands to suspend your computer. Additionally, instead of turning off
your screen via DPMS and/or displaying a black screen, i3lock displays
a white screen so you can see if your computer failed to resume from
suspend or if your screen is just locked. Also, when entering a wrong
password, i3lock does not call XBell(). This is important because
i3lock/slock think you've entered a password when resuming from suspend,
at least sometimes.