Fix links for book editions.

Now that there is one book to rule them all, some of the links needed updating.

The prose needed significant adjustment to accommodate the most recent changes.
I did my best to capture what is going on, but I am not confident it is correct.

src/rust-2018/documentation/new-editions-of-the-book.md

@@ -6,6 +6,8 @@
 
 ![Minimum Rust version: 1.28](https://img.shields.io/badge/Minimum%20Rust%20Version-1.28-red.svg) for drafts of the 2018 edition
 
+![Minimum Rust version: 1.31](https://img.shields.io/badge/Minimum%20Rust%20Version-1.31-brightgreen.svg) for the 2018 edition
+
 We've distributed a copy of "The Rust Programming Language," affectionately
 nicknamed "the book", with every version of Rust since Rust 1.0.
 
@@ -15,23 +17,19 @@ details were nailed down for the 1.0 release. It didn't do a fantastic job of
 teaching lifetimes.
 
 Starting with Rust 1.18, we shipped drafts of a second edition of the book.
-The final version was shipped with Rust 1.26. The new edition is a complete
+The final version was shipped with Rust 1.26. The second edition is a complete
 re-write from the ground up, using the last two years of knowledge we’ve
-gained from teaching people Rust. You’ll find brand-new explanations for a
-lot of Rust’s core concepts, new projects to build, and all kinds of other
-good stuff. Please [check it
-out](https://doc.rust-lang.org/book/second-edition/index.html) and let us
+gained from teaching people Rust.
+
+You can purchase [a dead-tree version of the second edition from No Starch
+Press](https://nostarch.com/Rust). Now that the print version has shipped, the
+second edition is frozen.
+
+As of 1.31, the book has been completely updated for the 2018 Edition release.
+It's still pretty close to the second edition, but contains information about
+newer features since the book's content was frozen. Additionally, instead of
+publishing separate editions of the book, only the latest version of the book
+is published online. You’ll find brand-new explanations for a lot of Rust’s
+core concepts, new projects to build, and all kinds of other good stuff.
+Please [check it out](https://doc.rust-lang.org/book/index.html) and let us
 know what you think!
-
-You can also purchase [a dead-tree version from No Starch
-Press](https://nostarch.com/Rust). Now that the print version has shipped,
-the second edition is frozen.
-
-The names are a bit confusing though, because the "second edition" of the
-book is the first printed edition of the book. As such, we decided that newer
-editions of the book will correspond with newer editions of Rust itself, and
-so starting with 1.28, we've been shipping drafts of the next version, [the
-2018 Edition](https://doc.rust-lang.org/book/2018-edition/index.html). It's
-still pretty close to the second edition, but contains information about
-newer features since the book's content was frozen. We'll be continuing to
-update this edition until we decide to print a second edition in paper.

src/rust-2018/trait-system/more-container-types-support-trait-objects.md

@@ -3,7 +3,7 @@
 ![Minimum Rust version: 1.2](https://img.shields.io/badge/Minimum%20Rust%20Version-1.2-brightgreen.svg)
 
 In Rust 1.0, only certain, special types could be used to create [trait
-objects](https://doc.rust-lang.org/book/second-edition/ch17-02-trait-objects.html).
+objects](https://doc.rust-lang.org/book/ch17-02-trait-objects.html).
 
 With Rust 1.2, that restriction was lifted, and more types became able to do this. For example,
 `Rc<T>`, one of Rust's reference-counted types:
@@ -14,7 +14,7 @@ use std::rc::Rc;
 trait Foo {}
 
 impl Foo for i32 {
-    
+
 }
 
 fn main() {
@@ -25,4 +25,4 @@ fn main() {
 This code would not work with Rust 1.0, but now works.
 
 > If you haven't seen the `dyn` syntax before, see the section on it. For
-> versions that do not support it, replace `Rc<dyn Foo>` with `Rc<Foo>`.
+> versions that do not support it, replace `Rc<dyn Foo>` with `Rc<Foo>`.