Update mailing list links

Author: José Valim

CONTRIBUTING.md

@@ -9,7 +9,7 @@ The issue tracker is the preferred channel for [bug reports](#bugs-reports),
 [features requests](#feature-requests) and [submitting pull
 requests](#pull-requests), but please **do not** use the issue tracker for
 personal support requests. Instead, use
-[the mailing list](http://groups.google.com/group/elixir-lang-core),
+[the mailing list](http://groups.google.com/group/elixir-lang-talk),
 [Stack Overflow](http://stackoverflow.com/questions/ask?tags=elixir), or
 [#elixir-lang](irc://chat.freenode.net/elixir-lang) on Freenode).
 

README.md

@@ -29,11 +29,13 @@ We appreciate any contribution to Elixir, so check out our [CONTRIBUTING.md](CON
 * #elixir-lang on freenode IRC
 * [Website][1]
 * [Issue tracker][2]
-* [Mailing list][3]
+* [elixir-talk Mailing list (for questions, general discussions)][3]
+* [elixir-core Mailing list (for announcements)][4]
 
   [1]: http://elixir-lang.org
   [2]: https://github.com/elixir-lang/elixir/issues
-  [3]: http://groups.google.com/group/elixir-lang-core
+  [3]: http://groups.google.com/group/elixir-lang-talk
+  [4]: http://groups.google.com/group/elixir-lang-core
 
 ## License