`IceCube::Schedule.from_ical` doesn't work with specific recurrence times.

[jorroll]

It seems highly likely that this is a known issue, but I can't seem to find a reference to it:

1. IceCube::Schedule can't seem to parse iCalendar strings that include specific recurrence times.

For example, the following does not work:

schedule = IceCube::Schedule.new(2.days.from_now) do |s|
    s.add_recurrence_time 3.days.from_now
end

#=> <IceCube::Schedule:0x0000000745f8d8 @start_time=Thu, 10 Aug 2017 13:41:33 UTC +00:00, @all_recurrence_rules=[#<IceCube::SingleOccurrenceRule:0x0000000745f270 @time=Fri, 11 Aug 2017 13:41:33 UTC +00:00>], @all_exception_rules=[]>

IceCube::Schedule.from_ical schedule.to_ical

#=> #<IceCube::Schedule:0x00000007465d50 @start_time=2017-08-10 13:41:33 UTC, @all_recurrence_rules=[], @all_exception_rules=[]>

Reading the schedule.to_ical using IceCubeSchedule.from_ical does not return the correct IceCube::Schedule object.

Thanks--awesome gem!

Using gem version 0.16.2 with ruby 2.4.1

[seejohnrun]

Thanks!
Fix coming in #408
I may end up pulling that fix out of that PR as well

[jorroll]

@seejohnrun Dang, you're on top of things! awesome!!!