Datetoken

- Feature: quarters
- Chore: Updated `pytz` dep from <2020.2,>=2018.04 to >=2018.04,<2020.5
- Chore: Updated `python-dateutil` dep from <2021.2,>=2018.04 to >=2018.04,<2021.4

- Updated `pytz` dep from <2020.2,>=2018.04 to >=2018.04,<2020.5

Added

- Token 'Y' as both snap and modifier behaviours. By Sighery

Changed

- Updated depedencies

Fixed

- Deprecation warnings from the usage of 'collections.Sequence'.

- Feature day of week snappers
- Dependency upgrades:
- pytz >= 2018.04 < 2019.04
- python-dateutil >= 2.7.3 < 2.8.2

- Updated dependencies:
- pytz
- freeegun
- python-dateutil