class Rufus::Scheduler::CronLine

level cron...
examining a whole year, that can take more than seconds for a seconds
#brute_frequency, on the other hand, will compute the frequency by

cron line.
Returns a quickly computed approximation of the frequency for this

def frequency
  return brute_frequency unless @seconds && @seconds.length > 1
  secs = toa(@seconds)
  secs[1..-1].inject([ secs[0], 60 ]) { |(prev, delta), sec|
    d = sec - prev
    [ sec, d < delta ? d : delta ]
  }[1]
end