minor #4101 [Contributing] extended Symfony 2.4 maintenance (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[Contributing] extended Symfony 2.4 maintenance

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

Maintenance for Symfony 2.4 has been extended from July 2014 to September 2014 (see [the blog post](http://symfony.com/blog/extended-maintenance-for-symfony-2-4)).

Commits
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92c67b5 [Contributing] extended Symfony 2.4 maintenance

contributing/community/releases.rst

@@ -86,29 +86,31 @@ Below is the schedule for the first few versions that use this release model:
 
 This results in very predictable dates and maintenance periods:
 
-+---------+---------+---------------------+-------------+
-| Version | Release | End of Maintenance  | End of Life |
-+=========+=========+=====================+=============+
-| 2.0     | 07/2011 | 03/2013 (20 months) | 09/2013     |
-+---------+---------+---------------------+-------------+
-| 2.1     | 09/2012 | 05/2013 (9 months)  | 11/2013     |
-+---------+---------+---------------------+-------------+
-| 2.2     | 03/2013 | 11/2013 (8 months)  | 05/2014     |
-+---------+---------+---------------------+-------------+
-| **2.3** | 05/2013 | 05/2016 (36 months) | 05/2017     |
-+---------+---------+---------------------+-------------+
-| 2.4     | 11/2013 | 07/2014 (8 months)  | 01/2015     |
-+---------+---------+---------------------+-------------+
-| 2.5     | 05/2014 | 01/2015 (8 months)  | 07/2015     |
-+---------+---------+---------------------+-------------+
-| 2.6     | 11/2014 | 07/2015 (8 months)  | 01/2016     |
-+---------+---------+---------------------+-------------+
-| **2.7** | 05/2015 | 05/2018 (36 months) | 05/2019     |
-+---------+---------+---------------------+-------------+
-| 2.8     | 11/2015 | 07/2016 (8 months)  | 01/2017     |
-+---------+---------+---------------------+-------------+
-| ...     | ...     | ...                 | ...         |
-+---------+---------+---------------------+-------------+
++---------+---------+--------------------------+-------------+
+| Version | Release | End of Maintenance       | End of Life |
++=========+=========+==========================+=============+
+| 2.0     | 07/2011 | 03/2013 (20 months)      | 09/2013     |
++---------+---------+--------------------------+-------------+
+| 2.1     | 09/2012 | 05/2013 (9 months)       | 11/2013     |
++---------+---------+--------------------------+-------------+
+| 2.2     | 03/2013 | 11/2013 (8 months)       | 05/2014     |
++---------+---------+--------------------------+-------------+
+| **2.3** | 05/2013 | 05/2016 (36 months)      | 05/2017     |
++---------+---------+--------------------------+-------------+
+| 2.4     | 11/2013 | 09/2014 (10 months [1]_) | 01/2015     |
++---------+---------+--------------------------+-------------+
+| 2.5     | 05/2014 | 01/2015 (8 months)       | 07/2015     |
++---------+---------+--------------------------+-------------+
+| 2.6     | 11/2014 | 07/2015 (8 months)       | 01/2016     |
++---------+---------+--------------------------+-------------+
+| **2.7** | 05/2015 | 05/2018 (36 months)      | 05/2019     |
++---------+---------+--------------------------+-------------+
+| 2.8     | 11/2015 | 07/2016 (8 months)       | 01/2017     |
++---------+---------+--------------------------+-------------+
+| ...     | ...     | ...                      | ...         |
++---------+---------+--------------------------+-------------+
+
+.. [1] Symfony 2.4 maintenance has been `extended to September 2014`_.
 
 .. tip::
 
@@ -179,4 +181,5 @@ version is published every two years and there is a year to upgrade.
 .. _Git repository: https://github.com/symfony/symfony
 .. _SensioLabs:     http://sensiolabs.com/
 .. _roadmap notification: http://symfony.com/roadmap
+.. _extended to September 2014: http://symfony.com/blog/extended-maintenance-for-symfony-2-4
 .. _timeline calculator: http://symfony.com/roadmap