updated versions in the README file

Author: fabpot

README.md

@@ -156,16 +156,16 @@ released under the MIT or BSD license.
 
 Enjoy!
 
-[1]:  http://symfony.com/doc/2.3/book/installation.html
+[1]:  http://symfony.com/doc/2.4/book/installation.html
 [2]:  http://getcomposer.org/
 [3]:  http://symfony.com/download
-[4]:  http://symfony.com/doc/2.3/quick_tour/the_big_picture.html
-[5]:  http://symfony.com/doc/2.3/index.html
-[6]:  http://symfony.com/doc/2.3/bundles/SensioFrameworkExtraBundle/index.html
-[7]:  http://symfony.com/doc/2.3/book/doctrine.html
-[8]:  http://symfony.com/doc/2.3/book/templating.html
-[9]:  http://symfony.com/doc/2.3/book/security.html
-[10]: http://symfony.com/doc/2.3/cookbook/email.html
-[11]: http://symfony.com/doc/2.3/cookbook/logging/monolog.html
-[12]: http://symfony.com/doc/2.3/cookbook/assetic/asset_management.html
-[13]: http://symfony.com/doc/2.3/bundles/SensioGeneratorBundle/index.html
+[4]:  http://symfony.com/doc/2.4/quick_tour/the_big_picture.html
+[5]:  http://symfony.com/doc/2.4/index.html
+[6]:  http://symfony.com/doc/2.4/bundles/SensioFrameworkExtraBundle/index.html
+[7]:  http://symfony.com/doc/2.4/book/doctrine.html
+[8]:  http://symfony.com/doc/2.4/book/templating.html
+[9]:  http://symfony.com/doc/2.4/book/security.html
+[10]: http://symfony.com/doc/2.4/cookbook/email.html
+[11]: http://symfony.com/doc/2.4/cookbook/logging/monolog.html
+[12]: http://symfony.com/doc/2.4/cookbook/assetic/asset_management.html
+[13]: http://symfony.com/doc/2.4/bundles/SensioGeneratorBundle/index.html