occurrences_between returns incorrect results if called with subseconds

[adamilan]

sc = IceCube::Schedule.new(Time.gm(2012,4,1,10,00))
sc.add_recurrence_rule IceCube::Rule.weekly
d = sc.occurrences_between(Time.gm(2012,5,1,10,00),Time.gm(2012,5,15))[0].subsec <<< == 0 > ok

d = sc.occurrences_between(Time.gm(2012,5,1,10,00,00,4),Time.gm(2012,5,15))[0].subsec <<< == 1/250000 > NOT OK<<<<

This issue can cause very difficult to find bugs when comparing occurrence dates with other dates
To work around it, before calling occurrences_between with parameters, I make sure that theres no milliseconds
t = t - t.subsec