Rust 1.29.2

# Traits

There is a new edition of the book and this is an old link.

> Traits abstract over behavior that types can have in common.

    pub trait Summarizable {
        fn summary(&self) -> String;
    }Run

Here are the relevant sections in the new and old books:

- In the second edition: Ch 10.02 — Traits
- In the second edition: Ch 19.03 — Advanced Traits
- In the first edition: Ch 3.19 — Traits