- update to 1.2.1:
* Readstat source updated to version 1.1.9
* introduced recognition for pandas datatype datetime64[ns,
UTC] and other datetime64 types when writing,
so that this column type gets correctly written as datetime
* introduced extra_datetime_formats and extra_date_formats
arguments for read functions, cleaned the list of
sas date, datetime and time formats to exclude those not
directly convertible to python objects
* improved performace of writer when there are datetime64
columns