Fix "ranges with steps" example, add note about "man 5 crontab"
Fix "ranges with steps" example, add note about "man 5 crontab"

healthchecks/healthchecks,healthchecks/healthchecks,healthchecks/healthchecks,iphoting/healthchecks,iphoting/healthchecks,healthchecks/healthchecks,iphoting/healthchecks,iphoting/healthchecks