Send SIGUSR1 to i3status to refresh after volume changes

NOTE: requires i3status >= v2.7

This still lags a bit, I'd really like much more responsive feedback. My
plan is to turn my old wmii plugins into a daemon that work side by side
with i3 to improve these kind of situations. Still need a good
notification mechanism on the bar though...

Also add consumption to the battery status since I'm upgrading i3status