Sled with Types instead of Bytes

This crate builds on top of sled and it's api is identical, except that it uses types in all places where sled would use bytes or it's IVec type. Types are binary encoded using bincode.

Example

    let db: sled::Db = sled::open("db")?;

    // The id is used by sled to identify which Tree in the database (db) to open.
    let animals = typed_sled::Tree::<String, Animal>::open(&db, "unique_id");

    let larry = "Larry".to_string();
    animals.insert(&larry, &Animal::Dog)?;

    assert_eq!(animals.get(&larry)?, Some(Animal::Dog));

Not tested throughoutly, in particular the Subscriber api might not be implemented correctly.