mention rustup.rs in README
@@ -92,8 +92,14 @@ strings.
First, install the latest stable version of
[Rust](https://www.rust-lang.org/en-US/install.html) using your
-preferred method. Then install Scryer Prolog with cargo,
-like so:
+preferred method. Scryer tends to use features from newer Rust
+releases, whereas Rust packages in Linux distributions, Macports,
+etc. tend to lag behind. [rustup](http://rustup.rs) will keep your
+Rust updated to the latest stable release; any existing Rust
+distribution should be uninstalled from your system before rustup is
+used.
+
+Scryer Prolog can be installed with cargo, like so:
```
$> cargo install scryer-prolog
