Fix some minor issues

README.md

@@ -19,6 +19,7 @@ release its source code.
     * Archives: <http://librelist.com/browser/libgit2/>
 * Website: <http://libgit2.github.com>
 * API documentation: <http://libgit2.github.com/libgit2>
+* IRC: #libgit2 on irc.freenode.net.
 
 What It Can Do
 ==================================
@@ -155,15 +156,7 @@ we can add it to the list.
 How Can I Contribute?
 ==================================
 
-Fork libgit2/libgit2 on GitHub, add your improvement, push it to a branch
-in your fork named for the topic, send a pull request. If you change the
-API or make other large changes, make a note of it in docs/rel-notes/ in a
-file named after the next release.
-
-You can also file bugs or feature requests under the libgit2 project on
-GitHub, or join us on the mailing list by sending an email to:
-
-libgit2@librelist.com
+Check the [contribution guidelines](CONTRIBUTING.md).
 
 
 License