Date, DateTime, Time and TimeWithZone can now be compared to infinity,
so it's now possible to create ranges with one infinite bound and
date/time object as another bound.
Ex.: @range = Range.new(Date.today, Float::INFINITY)
Also it's possible to check inclusion of date/time in range with
Ex.: @range.include?(Time.now + 1.year) # => true
@range.include?(DateTime.now + 1.year) # => true
Ability to create date/time ranges with infinite bound is required
for handling postgresql range types.