Jeff Kehres

Trying this out for monthly frequencies with an interval > 1 seems to get stuck in an infinite loop. I used the monthly test case from this PR and ran...

I don't think this PR is sufficient to fully support BYSETPOS. It only deals with monthly and yearly frequencies. However, playing around in the rrule.js demo [site](https://jakubroztocil.github.io/rrule/), BYSETPOS can have...

> I've pushed bysetpos support for weekly frequencies too. I don't think bysetpos makes sense with frequencies of daily, hourly, minutely, or secondly. RFC 5545 makes no mention of them,...

Using BYSECOND with MONTHLY does not work. I tried this: ```ruby ical = "RRULE:FREQ=MONTHLY;COUNT=4;BYSECOND=1,2,3,4;BYSETPOS=2" schedule = IceCube::Schedule.from_ical(ical) schedule.start_time = Time.new(2015, 5, 28, 12, 0, 0) schedule.occurrences_between(Time.new(2015, 01, 01), Time.new(2017, 01,...