Readme: Newer Nightly Version, Mention Rustup

Author: killercup

README.md

@@ -10,26 +10,32 @@ I currently recommend that you install [multirust][multirust] and then use it to
 install the current rustc nightly version that works with Miri:
 
 ```sh
-multirust update nightly-2016-04-05
+multirust update nightly-2016-04-11
 ```
 
 ## Build
 
 ```sh
-multirust run nightly-2016-04-05 cargo build
+multirust run nightly-2016-04-11 cargo build
 ```
 
 ## Run a test
 
 ```sh
-multirust run nightly-2016-04-05 cargo run -- \
-  --sysroot $HOME/.multirust/toolchains/nightly-2016-04-05 \
+multirust run nightly-2016-04-11 cargo run -- \
+  --sysroot $HOME/.multirust/toolchains/nightly-2016-04-11 \
   test/filename.rs
 ```
 
-If you installed without using multirust, you'll need to adjust the command to
-run your cargo and set the `sysroot` to the directory where your rust compiler
-is installed (`$sysroot/bin/rustc` should be a valid path).
+If you are using [rustup][rustup] (the name of the multirust rewrite in Rust),
+the `sysroot` path will also include your build target (e.g.
+`$HOME/.multirust/toolchains/nightly-2016-04-11-x86_64-apple-darwin`). You can
+see the current toolchain's directory by running `rustup which cargo` (ignoring
+the trailing `/bin/cargo).
+
+If you installed without using multirust or rustup, you'll need to adjust the
+command to run your cargo and set the `sysroot` to the directory where your
+Rust compiler is installed (`$sysroot/bin/rustc` should be a valid path).
 
 ## License
 
@@ -49,3 +55,4 @@ additional terms or conditions.
 [mir]: https://github.com/rust-lang/rfcs/blob/master/text/1211-mir.md
 [usask]: https://www.usask.ca/
 [multirust]: https://github.com/brson/multirust
+[rustup]: https://www.rustup.rs