add tests from https://github.com/nst/JSONTestSuite

[thedufer]

I came across https://github.com/nst/JSONTestSuite and thought I should test jsonaf on them. It identifies a bunch of things that shouldn't parse but do. I think a lot of it is because we make no attempt to validate the contents of strings or numbers (as long as they consist of the right character sets). There are some that look potentially interesting, though, like "n_structure_single_star.json" which contains "*" (no quotes) and parses to `Number "*".

Not sure if you think this is worth merging.