changed version from 2.3.0 --> 2.3.7

just for convenience (i.e. people not reading the text carefully but copying the example and starting with an "old" Symfony version)

Author: luebbert42

book/installation.rst

@@ -57,11 +57,11 @@ Distribution:
 
 .. code-block:: bash
 
-    $ php composer.phar create-project symfony/framework-standard-edition /path/to/webroot/Symfony 2.3.0
+    $ php composer.phar create-project symfony/framework-standard-edition /path/to/webroot/Symfony 2.3.7
 
 .. tip::
 
-    For an exact version, replace "2.3.0" with the latest Symfony version.
+    For an exact version, replace "2.3.7" with the latest Symfony version.
     For details, see the `Symfony Installation Page`_
 
 .. tip::