Initial rewrite to module-based, with TODOs left

Closes #3 and closes #5 because the API is totally new and these issues are no longer present.

Closes #4, closes #6, closes #10, and closes #11 by removing talk of implementation strategies.

Closes #8 by no longer talking about brand checked methods; all methods will exist.

Closes #13 by being clear this is for when you aren't running first.

Closes #19 by implementing the discussion there.