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Release date was August 1st, 2019
first beta release (but still work in progress)
migration to python 3.4, 3.5, 3.6 and 3.7
automated code review
100% test coverage
finished docs
removed many calculation functions
(BusinessDate.add_years, etc),
better use `+` or `-` instead
made some static methods to instance methods
(BusinessDate.days_in_month, BusinessDate.end_of_month, BusinessDate.end_of_quarter)
swapped the order of arguments in `BusinessDate.diff_in_ymd`
new __cmp__ paradigm
adding max_days and min_day method to `BusinessPeriod`