explicitly mention beta and nightly

Author: steveklabnik

src/editions/index.md

@@ -45,6 +45,24 @@ advantage of such features.
 ## Trying out the 2018 edition
 
 At the time of writing, there are two editions: 2015 and 2018. 2015 is today's
-Rust; Rust 2018 will ship later this year. To transition to the 2018 edition
-from the 2015 edition, you'll want to get started with the [transition
-section](transitioning-an-existing-project-to-a-new-edition.html).
+Rust; Rust 2018 is currently in beta, and will land in stable in Rust 1.31, on December 6, 2018.
+
+To give the 2018 edition a try, install the beta toolchain:
+
+```console
+> rustup install beta
+````
+
+If you want the really bleeding edge, you can try nightly:
+
+```console
+> rustup install nightly
+```
+
+When you see commands like `cargo fix` elsewhere in this guide, you may
+need to preface them with the toolchain:
+
+```console
+> cargo +beta fix --edition
+> cargo +nightly fix --edition
+```