To kill boilerplate error handling, add a couple must* convenience functions (Parse{Int,Uint,Float}) and a mustWriter. All panic on error.
[unmarshal] Allow lax decoding of dates. Never try to TextUnmarshal a time.Time (as this interferes with lax decoding).
[decode] Add mustParseBool and use the mustParse* family for lax decoding.
[tests] Enhance the tests: All four formats, finer-grained decode testing, test everything we possibly can.