Added an implementation of NearestDayOfWeek() in Time::Moment::Adjusters.
Fix Time::Moment->from_epoch when called with a floating-point value whose fractional part rounds to exactly 1.000000000 seconds at 9 decimal digits. Such values previously caused a “Parameter 'nanosecond' is out of the range [0, 999_999_999]” error; they are now normalized by incrementing the second and wrapping nanoseconds to zero, consistent with the rd/jd/mjd constructors. Reported by @butzsch, addressing issue #40.