MDBook Rust

Enhanced Rust support for MDBook.

Any chapters written as Rust source files will be translated to Markdown, allowing you to test your book as a Rust crate. It's like literate programming in reverse (illiterate programming).
Everything else is left alone.

This Rust code:

fn body() {
    // # Heading
    //
    // Paragraph text.
    some_code();
}

will be converted to:

# Heading

Paragraph text.

```rust,ignore
some_code();
```

See examples/book for a complete example.