Put version into quotes, otherwise it fails

dannykopping · dannykopping · commit 6dc62a80e02a · 2014-08-05T16:21:50.000+02:00
When using the `zsh` shell, the command fails because of:

```
$ composer create-project symfony/framework-standard-edition myproject/ ~2.5
zsh: no such user or named directory: 2.5
```

This problem does not occur in Bash.
Quoting the version number does not effect Bash, and fixes ZSH.
diff --git a/quick_tour/the_big_picture.rst b/quick_tour/the_big_picture.rst
@@ -18,7 +18,7 @@ directory:
 
 .. code-block:: bash
 
-    $ composer create-project symfony/framework-standard-edition myproject/ ~2.5
+    $ composer create-project symfony/framework-standard-edition myproject/ '~2.5'
 
 .. note::
 
