0.2.2:
 * update notification with battery level as it changes
 * close and destroy notification when killed
 * command-line options to control check frequency
 * command-line option: -f: fork off and die
 * periodically re-check which batteries are connected

0.2.1:
 * bug: sometimes doesn't notify
 * bug: DESTDIR doesn't work properly in makefile

0.2.0:
 * take warn levels as command-line arguments
 * stop notifications from expiring