update readme with package.el installation steps

Author: mpenet

src/etc/emacs/README.md

@@ -29,10 +29,12 @@ 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
+### package.el installation via Marmalade
 
 It can be more convenient to use Emacs's package manager to handle
-installation for you if you use many elisp libraries.
+installation for you if you use many elisp libraries. If you have
+package.el but haven't added Marmalade, the community package source,
+yet, add this to ~/.emacs.d/init.el:
 
 ```lisp
 (require 'package)
@@ -41,12 +43,10 @@ installation for you if you use many elisp libraries.
 (package-initialize)
 ```
 
-```lisp
-(require 'package)
-(add-to-list 'package-archives
-             '("melpa" . "http://melpa.milkbox.net/packages/") t)
-(package-initialize)
-```
+Then do this to load the package listing:
+
+* <kbd>M-x eval-buffer</kbd>
+* <kbd>M-x package-refresh-contents</kbd>
 
 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.
@@ -56,6 +56,17 @@ 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 so the version there (1.7.1) is very outdated.
 
+From there you can install rust-mode or any other modes by choosing
+them from a list:
+
+* <kbd>M-x package-list-packages</kbd>
+
+Now, to install packages, move your cursor to them and press i. This
+will mark the packages for installation. When you're done with
+marking, press x, and ELPA will install the packages for you (under
+~/.emacs.d/elpa/).
+
+* or using <kbd>M-x package-install rust-mode
 
 #### Important