Changes:
* Fix error message in get_all_records
* Auto resizing is now available for rows
* add new method to hide/show a worksheet
* Download PDF from Spreadsheet
* Add test on auto_resize_columns
* Add method to unmerge cells
* Add method to delete a protected range
* Feature/clean organize documentation
* Add warning about deprecated oauth flow
* Add new batch_format method.
* Encode string to utf-8 when importing CSV content
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