MODFLOW developer tools 0.3.0

This update gives download.download_and_unzip() a return value, the Path the archive was extracted to. Also remove all package dependencies (previously numpy and pytest were required, now optional).

Refactoring

• refactor(dependencies): Remove them, update readme (#95). Committed by w-bonelli on 2023-08-04.
• refactor(download_and_unzip): Return path to extract locn (#96). Committed by w-bonelli on 2023-08-04.