Add fuzzing tests

[langston-barrett]

Brainstorm what functions could accept []bytes and test with fuzzing. Initially:

• tabular could do a lot
• checklistFromBytes

Here's a good fuzzing package: https://github.com/dvyukov/go-fuzz#go-fuzz-randomized-testing-for-go

Fuzzing could also be used for failing inputs for checks, e.g., giving invalid/failing input.