Encoder might not differentiate floats from integers in map keys

[tliron]

See this playground example.

This would create problems for roundtrips. Decoding works correctly for "1.0", but the the resulting encoding, if decoded again, would result in an integer rather than a float.

[philomory]

Forget map keys, the encoder doesn't differentiate floats with no fractional part from integers in any context (although, the decoder does). This is because the encoder renders floats with Go's standard strconv.FormatFloat, for which no combination of arguments will grant the desired output in all cases. Further, per #430, the developers seem to think this is a good thing. Personally my reading of the YAML spec disagrees, but the YAML spec is frustratingly vague on the point.