Rust 1.29.2

# Documentation

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

> Documentation comments use `///` instead of `//` and support Markdown notation for formatting the text if you’d like. You place documentation comments just before the item they are documenting.

    /// Adds one to the number given.
    ///
    /// # Examples
    ///
    /// ```
    /// let five = 5;
    ///
    /// assert_eq!(6, my_crate::add_one(5));
    /// ```
    pub fn add_one(x: i32) -> i32 {
        x + 1
    }Run

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

- In the second edition: Ch 14.02 — Publishing to crates.io, section Making useful documentation
- In the first edition: Ch 4.4 — Documentation