update readme

Author: mpenet

src/etc/emacs/README.md

@@ -4,7 +4,10 @@ rust-mode: A major emacs mode for editing Rust source code
 `rust-mode` makes editing [Rust](http://rust-lang.org) code with emacs
 enjoyable.
 
-To install, check out this repository and add this to your .emacs
+
+### Manual Installation
+
+To install manually, check out this repository and add this to your .emacs
 file:
 
     (add-to-list 'load-path "/path/to/rust-mode/")
@@ -25,3 +28,49 @@ it, and pressing `C-j`:
 
 Rust mode will automatically be associated with .rs and .rc files. To
 enable it explicitly, do `M-x rust-mode`.
+
+### package.el installation via Marmalade or Melpa
+
+It can be more convenient to use Emacs's package manager to handle
+installation for you if you use many elisp libraries.
+
+```lisp
+(require 'package)
+(add-to-list 'package-archives
+             '("marmalade" . "http://marmalade-repo.org/packages/"))
+(package-initialize)
+```
+
+```lisp
+(require 'package)
+(add-to-list 'package-archives
+             '("melpa" . "http://melpa.milkbox.net/packages/") t)
+(package-initialize)
+```
+
+If you use a version of Emacs prior to 24 that doesn't include
+package.el, you can get it from http://bit.ly/pkg-el23.
+
+If you have an older ELPA package.el installed from tromey.com, you
+should upgrade in order to support installation from multiple sources.
+The ELPA archive is deprecated and no longer accepting new packages,
+so the version there (1.7.1) is very outdated.
+
+
+#### Important
+
+In order to have cm-mode properly initialized after compilation prior
+to rust-mode.el compilation you will need to add these `advices` to
+your init file or if you are a melpa user install the `melpa` package.
+
+```lisp
+(defadvice package-download-tar
+  (after package-download-tar-initialize activate compile)
+  "initialize the package after compilation"
+  (package-initialize))
+
+(defadvice package-download-single
+  (after package-download-single-initialize activate compile)
+  "initialize the package after compilation"
+  (package-initialize))
+```