Unify roundtrip and roundtripEffect

[1Jajen1]

I had both methods split previously but that was not necessary.

roundtrip tests an encode and decode function to see if decode . encode == id holds. It also allows for applicative effects in the decode function. This allows the decoder to return e.g. Either/Option/... to indicate failure or other effects while decoding.

roundtripEffect is basically the same thing, but adds the possibility of effects M in the decode and encode functions. This allows to for example define a roundtrip property for writing to and reading from a file.

In the event of failure roundtrip shows the intermediate value (after encoding) and a diff of the initial value and the value produced by decode.

[rachelcarmena]

🎉