Htimeseries

==================

- Worked around an old Pandas bug related to time zones
(https://github.com/pandas-dev/pandas/issues/11736) in order to
maintain compatibility with Pandas 0.23 (the bug was fixed in Pandas
0.24).

==================

- Fixed packaging error where it didn't install dependency
backports.zoneinfo on Python<3.9.

==================

- The timestamps of the dataframe index are now aware. When initializing
a ``HTimeseries`` object with a dataframe, the dataframe index
timestamps must be aware. When initializing with a filelike object,
either the filelike object must contain a ``timezone`` header or the
new ``default_tzinfo`` parameter must be specified.

==================

- Fixed incompatibility with pandas 1.2.

==================

- When reading a time series from a file-like object, it is now
permitted for it to not have a flags column. In this case, an empty
flags column is automatically added to the HTimeseries object.

==================

- Only Python>=3.7 is now supported.
- When reading or writing a time series, it now checks that there are no
duplicate timestamps and raises an exception if there are.