IterTable 2.1

IterTable 2.1 brings compatibility with the latest Python versions, as well as several improvements for integration with Django Data Wizard 2.0. All changes by @sheppard.

API Improvements

• Support loading data from arbitrary file-like sources, such as S3 (wq/django-data-wizard#31)
• Raise an error by default when loading a nonexistent file (wq/django-data-wizard#33)
• Option to load all sheets from workbook at once (by setting sheet_name=None) (98b994e, f67a908)
• Detect application/csv in addition to text/csv (acb9fa7)

Ecosystem Updates

• Support Python 3.10 (7d1a814; wq/django-data-wizard#37)
• Drop all remaining support for Python 2 (475eb6c)
• Leverage openpyxl instead of xlrd when parsing XLSX format (475eb6c)