Update book for rustup

Author: brson

src/doc/book/getting-started.md

@@ -113,19 +113,30 @@ tier 3 platforms that will ever be!
 
 ## Installing Rust
 
-All we need to do is open a terminal and type this:
+All you need to do on Unix systems like Linux and macOS is open a
+terminal and type this:
 
 ```bash
 $ curl https://sh.rustup.rs -sSf | sh
 ```
 
-This will download a script, and start the installation. If it all goes well,
-you’ll see this appear:
+It will download a script, and start the installation. If everything
+goes well, you’ll see this appear:
 
 ```text
 Rust is installed now. Great! 
 ```
 
+Installing on Windows is nearly as easy: download and run
+[rustup-init.exe]. It will start the installation in a console and
+present the above message on success.
+
+For other installation options and information, visit the [install]
+page of the Rust website.
+
+[rustup-init.exe]: https://win.rustup.rs
+[install]: https://www.rust-lang.org/install.html
+
 ## Uninstalling
 
 Uninstalling Rust is as easy as installing it:
@@ -146,12 +157,15 @@ You should see the version number, commit hash, and commit date.
 
 If you do, Rust has been installed successfully! Congrats!
 
-If you don't and you're on Windows, check that Rust is in your %PATH% system
-variable: `$ echo %PATH%`. If it isn't, run the installer again, select "Change"
-on the "Change, repair, or remove installation" page and ensure "Add to PATH" is
-installed on the local hard drive.  If you need to configure your path manually,
-you can find the Rust executables in a directory like
-`"C:\Program Files\Rust stable GNU 1.x\bin"`.
+If you don't, that probably means that the `PATH` environment variable
+doesn't include Cargo's binary directory, `~/.cargo/bin` on Unix, or
+`%USERPROFILE%\.cargo\bin` on Windows. This is the directory where
+Rust development tools live, and most Rust developers keep it in their
+`PATH` environment variable, which makes it possible to run `rustc` on
+the command line. Due to differences in operating systems, command
+shells, and bugs in installation, you may need to restart your shell,
+log out of the system, or configure `PATH` manually as appropriate for
+your operating environment.
 
 Rust does not do its own linking, and so you’ll need to have a linker
 installed. Doing so will depend on your specific system. For