Add isless to allow easy sorting

v0.0.6

Enable additional isless tests

Improve ZonedDateTime handling

Adds astimezone(::AbstractInterval{ZonedDateTime}) to make dealing with time zones easier. Also makes a couple of minor improvements to readability of print(::AbstractInterval).

Fix AnchoredInterval comparisons

Fixes a bug in which comparisons between two AnchoredIntervals ignored Inclusivity values

Improve comparison operators

Simplifies and standardizes set operations (intersect, issubset)

Distinguishes between less-than (<) and less-than-and-disjoint (≪)

Add improved Interval constructors

Add isopen, isclosed, and the following constructors to simplify specifying Inclusivity:

• Interval(first, last, include_first::Bool, include_last::Bool)
• AnchoredInterval{P}(anchor, include_first::Bool, include_last::Bool)

Initial release

v0.0.1

Update TimeZones version requirement