Merge pull request #163 from durka/patch-4

rustup migration instructions

README.md

@@ -1,4 +1,4 @@
-**Note: multirust is not actively maintained. Migrate to [rustup.rs](https://github.com/rust-lang-nursery/rustup.rs).**
+**Note: multirust is not actively maintained. Migrate to [rustup.rs](https://github.com/rust-lang-nursery/rustup.rs) ([help](#migrating-to-rustup)).**
 
 [![Build Status](https://travis-ci.org/brson/multirust.svg?branch=master)](https://travis-ci.org/brson/multirust)
 
@@ -293,3 +293,13 @@ quite meager though so it's unlikely to help.
 
 multirust is licensed under the same terms as the Rust compiler, now and
 forevermore.
+
+# Migrating to rustup
+
+If you have multirust installed and you would like to migrate to rustup.rs,
+follow these steps (for Linux/Mac):
+
+1. First, uninstall Multirust using the instructions given [above](#quick-installation).
+2. Delete the folder `~/.multirust`.
+3. If the file `/usr/local/lib/rustlib/uninstall.sh` still exists, the uninstallation was not successful. Run `sudo /usr/local/lib/rustlib/uninstall.sh` to complete it.
+4. Install rustup using the instructions at [rustup.rs](https://www.rustup.rs/).