Gspread-asyncio

- Drop support for Python 3.5.
- Add missing folder_id argument to Client.create(). Thanks to azjps for the patch!
- Document how to use gspread_asyncio with google-auth. Thanks to kraptor for the patch!

- Fix bug with clearing of caches when deleting spreadsheets and worksheets
- Add PEP-484 function signature type hints to the API
- Remove setup.py dependency on oauth2client. gspread 3.6 allows you to use objects from the new google.auth library.
- Miscellaneous documentation fixes

New APIs:
- add_protected_range
- append_rows
- batch_get
- batch_update
- insert_rows

Thanks to Egor Panfilov for the implementation.

Other minor changes:
- Fixes to documentation
- Internally use the post-Python 3.7 asyncio APIs when appropriate