Rework Option Parsing

[lishaduck]

I realized if you rebase-merge the end of the stack, I think GH should mark all the PRs as merged.

• refactor: centralize AppState #375
• refactor: drop abstractions that make options evaluate lazily #376
• refactor: centralize into functions #377
• Refactor process.cwd calls #382
• Start Moving Tests to JS #381

[lishaduck]

@jfmengels, I'm done for the night; those PRs are ready for review whenever you are!

(School's starting tomorrow, so I wanted to get in a batch before I get busy; know that my availability will be low for at least a few days)