foreach for string[string]AA

[Anton Pastukhov via Digitalmars-d-learn]

I can't see the logic in AA foreach order. Consider this code:

```
void main() {
    string[string] test = [
        "one": "1",
        "two": "2",
        "three": "3",
        "four": "4"
    ];

    import std.stdio:writeln;

    foreach(k, v; test) {
        writeln(k);
    }
}

Output:
three
two
one
four

I was sure output should be
one
two
three
four