Draft: Version 2.0.0: Ability to customize head/body, testing, and CI

This release adds:

• Integration and unit tests (#10)
• Ability to set a custom head and body (#1 and #2)

It changes the following:

• Refactor the CLI into a separate module in preparation for GUI (#11)
• Refactors constants and helper classes into separate files

To do:

• Unit tests
• Integration tests
• Ability to change head
• Ability to change body