Hash stability

[prataprc]

Values in jsondata::Json should not change in its hash value for any given hashing algorithm. Also the serialized form of jsondata::Json should not affect its hash value for any give hashing algorithm.

List of common hashing algorithm:

fasthash::city
fasthash::murmur3
SHA1

[Roenbaeck]

Json currently does not implement Hash. Given that it's internally sorted, from what I understand, I added this impl.

impl Hash for Json{
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.to_string().hash(state);
    }
}

Under what circumstances would two semantically equal JSON documents produce different hashes using this approach?

[prataprc]

to_string is part of ToString trait, which in turn is consumed by fmt::Display, which is meant for human consumption of data. So we cannot make any guarantees on the output of ToString, it might change later.