Determine how intervals relate to each other.
time
usage as it is no longer necessary by @DeedleFake in https://github.com/francesconi/go-rampart/pull/2
Full Changelog: https://github.com/francesconi/go-rampart/compare/v0.3.0...v0.4.0
NewIntervalFunc
to allow relating any types as long as a comparison function is providedtime.Time