Changed Rust Book versions in links to 2018

Forgot to add changes to last commit.

exercises/error_handling/README.md

@@ -1,5 +1,5 @@
-For this exercise check out the chapters:
+For this exercise check out the sections:
-- [Error Handling](https://doc.rust-lang.org/book/second-edition/ch09-02-recoverable-errors-with-result.html) 
+- [Error Handling](https://doc.rust-lang.org/book/2018-edition/ch09-02-recoverable-errors-with-result.html) 
-- [Generics](https://doc.rust-lang.org/book/second-edition/ch10-01-syntax.html) 
+- [Generics](https://doc.rust-lang.org/book/2018-edition/ch10-01-syntax.html) 
 
 of the Rust Book.

exercises/functions/REAMDE.md

@@ -1 +1 @@
-For this exercise check out the chapter [Functions](https://doc.rust-lang.org/book/second-edition/ch03-03-how-functions-work.html) of the Rust Book.
+For this exercise check out the chapter [Functions](https://doc.rust-lang.org/book/2018-edition/ch03-03-how-functions-work.html) of the Rust Book.

exercises/if/REAMDE.md

@@ -1 +1 @@
-For this exercise check out the chapter [If](https://doc.rust-lang.org/book/second-edition/ch03-05-control-flow.html) of the Rust Book.
+For this exercise check out the chapter [If](https://doc.rust-lang.org/book/2018-edition/ch03-05-control-flow.html?highlight=control,fl#control-flow) of the Rust Book.

exercises/macros/README.md

@@ -1,2 +1,2 @@
-For this exercise check out the section [Macros](https://doc.rust-lang.org/book/first-edition/macros.html) and the chapter
+For this exercise check out the section [Macros](https://doc.rust-lang.org/book/2018-edition/macros.html) and the chapter
 [Macros Appendix](https://doc.rust-lang.org/book/2018-edition/appendix-04-macros.html) of the Rust Book and [The Little Book of Rust Macros](https://danielkeep.github.io/tlborm/book/index.html). 

exercises/modules/README.md

@@ -1 +1 @@
-For this exercise check out the [Modules](https://doc.rust-lang.org/book/second-edition/ch07-01-mod-and-the-filesystem.html) chapter of the Rust Book.
+For this exercise check out the [Modules](https://doc.rust-lang.org/book/2018-edition/ch07-01-mod-and-the-filesystem.html) chapter of the Rust Book.

exercises/move_semantics/README.md

@@ -1,7 +1,7 @@
 These exercises are adapted from [pnkfelix](https://github.com/rustlings/rustlings/blob/master)'s [Rust Tutorial](https://pnkfelix.github.io/rust-examples-icfp2014/) -- Thank you Felix!!!
 
 For this exercise check out the chapters:
-- [Ownership](https://doc.rust-lang.org/book/second-edition/ch04-01-what-is-ownership.html)
+- [Ownership](https://doc.rust-lang.org/book/2018-edition/ch04-01-what-is-ownership.html)
-- [Reference and borrowing](https://doc.rust-lang.org/book/second-edition/ch04-02-references-and-borrowing.ht)
+- [Reference and borrowing](https://doc.rust-lang.org/book/2018-edition/ch04-02-references-and-borrowing.html)
 
 of the Rust Book.

exercises/primitive_types/README.md

@@ -0,0 +1 @@
+For this exercise check out the chapter [Data Types](https://doc.rust-lang.org/book/2018-edition/ch03-02-data-types.html) of the Rust Book.

exercises/standard_library_types/README.md

@@ -1 +1,5 @@
-For this exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/second-edition/ch16-03-shared-state.html) of the Rust Book.
+For the Arc exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/2018-edition/ch16-03-shared-state.html) of the Rust Book.
+
+For the Iterator exercise check out the chapters [Iterator](https://doc.rust-lang.org/book/2018-edition/ch13-02-iterators.html) of the Rust Book and the [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/trait.Iterator.htmlj).
+Do not adjust your monitors-- iterators 1 and 2 are indeed missing. Iterator 3 is a bit challenging so we're leaving space for some exercises to lead up to it!
+

exercises/strings/REAMDE.md

@@ -0,0 +1 @@
+For this exercise check out the chapter [Strings](https://doc.rust-lang.org/book/2018-edition/ch08-02-strings.html) of the Rust Book.

exercises/tests/README.md

@@ -1,3 +1,3 @@
 Going out of order from the book to cover tests -- many of the following exercises will ask you to make tests pass!
 
-For this exercise check out the section [How to Write Tests](https://doc.rust-lang.org/book/second-edition/ch11-01-writing-tests.html) of the Rust Book.
+For this exercise check out the section [How to Write Tests](https://doc.rust-lang.org/book/2018-edition/ch11-01-writing-tests.html) of the Rust Book.

exercises/threads/README.md

@@ -1 +1 @@
-For this exercise check out the [Dining Philosophers example](https://doc.rust-lang.org/1.4.0/book/dining-philosophers.html) and the chapter [Concurrency](https://doc.rust-lang.org/book/second-edition/ch16-01-threads.html) of the Rust Book.
+For this exercise check out the [Dining Philosophers example](https://doc.rust-lang.org/1.4.0/book/dining-philosophers.html) and the chapter [Concurrency](https://doc.rust-lang.org/book/2018-edition/ch16-01-threads.html) of the Rust Book.

exercises/variables/README.md

@@ -0,0 +1 @@
+For this exercise checkout the section [Variables and Mutability](https://doc.rust-lang.org/book/2018-edition/ch03-01-variables-and-mutability.html) of the Rust Book.