Update GETTING_STARTED.md
Fix broken link to the docs.
@@ -6,7 +6,7 @@ an exact match.
The following steps assume that you are in the same directory as the exercise.
You must have rust installed.
-Follow the [Installing Rust chapter in the Rust book](http://doc.rust-lang.org/stable/book/installing-rust.html).
+Follow the [Getting Started chapter in the Rust book](https://doc.rust-lang.org/stable/book/getting-started.html).
The [Rust language section](http://exercism.io/languages/rust)
section from exercism is also useful.
