Debian 9.4 does not install `psmisc` by default and the following error will happen during installation: ``` [✗] /usr/local/bin/pihole: line 353: killall: command not found /usr/local/bin/pihole: line 364: killall: command not found ``` This patch adds `psmisc` (that contains `killall`) as dependency Signed-off-by: Michele Bologna <michele.bologna@gmail.com>