refactor: split out modules for separate concerns

[wpbonelli]

trafficstars

• organize the codebase into modules
• use absolute instead of relative imports
• no need for classes to inherit from object
• use consistent camel case for class names
• remove imports from __future__ from test script (not needed)
• run black and isort on python files (responsible for LOC increase)
• add .DS_Store to .gitignore
• miscellaneous tidying

This should not introduce any functional changes — see passing tests on my fork

todo: tests to pytest