Gsheets

------------------------------

-------------

Drop Python 3.6 support.

-----------

Drop Python 2 support.

Fix loading of sheets that contain worksheets with titles that are also a valid
reference in A1-notation (add quoting, GH 21).

Drop Python 3.5 support and tag Python 3.9 and 3.10 support.

Changed a few optional flags to keyword-only arguments.

Migrate CI to GitHub actions and extend build matrix.

-------------

Avoid ``file_cache`` import warning with oauth2client >= 4.

-----------

Add support for API key auth: add optional ``developer_key`` argument to
``Sheets`` constructor and alternate ``Sheets.from_developer_key()``
constructor, see also
https://developers.google.com/sheets/api/guides/authorizing (PR Natarajan
Krishnaswami).

Improve test and doc building config.

-------------

Fix documentation example of ``make_filename``.

Tag Python 3.7 and 3.8 support.