Rust 1.30.0

# `type` aliases

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

> Rust provides the ability to declare a type alias with the `type` keyword to give an existing type another name.

    type Kilometers = i32;Run

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

- In the second edition: Ch 19.04 — Advanced Types, section Type Synonyms
- In the first edition: Ch 3.28 — `type` aliases