Refactor ZoningSystem

[wsp-mbuckley]

Describe Changes

Refactor the ZoningSystem class, update how the data is stored and how to access it. Resolves #15.

Task Checklist

• [ ] Have unittests been added (testing individual functions and their edge cases)
• [ ] Have integration tests been added (if applicable, to test modules of functionality)
• [ ] Updated RELEASE.md to reflect changes in PR
• [ ] Have new dependencies been added?
  • [ ] Have they been added to either requirements.txt or requirements_dev.txt.
  • [ ] Have they been added to setup.cfg

[wsp-mbuckley]

Resolves #5

[wsp-mbuckley]

Resolves #16