Use melpa-stable as an additional package source

Permits installation of htmlize
(see
https://www.fun-mooc.fr/courses/course-v1:inria+41016+session01bis/discussion/forum/47b48c40e908418866d5dbcb2079e22e7b4b9623/threads/5bd33084a0241eb2d5005d50)

module2/ressources/rr_org/init.el

@@ -50,6 +50,9 @@
 ;;   (setenv "JVM_OPTS" (concat "-Dhttp.proxyHost=" proxy-name
 ;;                              " -Dhttp.proxyPort=" proxy-port)))
 
+(add-to-list 'package-archives
+		 '("melpa-stable" . "http://stable.melpa.org/packages/"))
+
 (require 'org)
 
 (require 'ess-site)

module2/ressources/rr_org/init.org

@@ -74,6 +74,12 @@ document, simply =M-x org-babel-tangle=.
 ;;                              " -Dhttp.proxyPort=" proxy-port)))
 #+end_src
 
+* Package sources
+** Use melpa-stable
+#+BEGIN_SRC emacs-lisp :tangle init.el
+(add-to-list 'package-archives
+		 '("melpa-stable" . "http://stable.melpa.org/packages/"))
+#+END_SRC
 * Loading files:  
 ** Loading babel: 						     :ARNAUD:
 #+begin_src emacs-lisp :tangle init.el