reference /var/lib/systemd/timers in manpage
rework generator manpage for consistency with systemd builtin generators
forcefully restart all units on file updates
inhibit /etc/cron.boot/ after first execution (issue #30)
issue #30: update readme
don't run mail_on_failure as root
crontab: makes -l/-r/-e mutually exclusive
crontab: act as expected by deluser; don't show it in crontab --help