This is very very good. Only thing I can think that it's missing (and maybe you have support for this and I misread your readme) is ordered maps (there's a better name for this but I'm blanking).

For example, imagine I have a compact append only map format and I want to represent it like this (where last tuple wins when you have a duplicate key, but earlier history is preserved)

    {
     score: 0,
     score: 1
    }