Consider using Vinyl records

[scott-fleischman]

I find myself modifying the open-ended Token type by stripping marks, removing case and other similar operations. It caused a lot of runtime issues that would have been better caught at type-checking time.

@jonsterling's Vinyl records may be useful here to encode marks as separate records and be more precise in type signatures about which marks are expected to be present or not present without having to specify a new Token record type for every combination of marks that we need.