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* Thanks to nolanbconaway for their contributions!
* New methods to handle relations between months:
* ``month.to(other)`` for generating intervals of months.
* ``month.distance(other)`` for computing distance between months.
* New methods for month date info
* ``month.n_days`` to return the number of days in the month.
* ``month.dates`` to return a list of all days in the month.
* ``month.nth(day)`` to return a specific day in the month.
* ``__int__`` and ``__float__`` methods added.
* Also a ``month.gregorian_month_number`` method to compute number of months
since year 0.