minor symfony#3732 Update routing.rst. Explain using url() v. path(). (ackerman)

This PR was submitted for the 2.4 branch but it was merged into the 2.3 branch instead (closes symfony#3732).

Discussion
----------

Update routing.rst. Explain using url() v. path().

The original documentation seemed to imply that, when generating absolute URLs from a template, the argument TRUE should be supplied to the url() method. This change explains that in Twig, one uses the url() method to generate an absolute URL.

Commits
-------

6eac303 Update routing.rst. Explain using url() v. path().

Author: weaverryan

book/routing.rst

@@ -1240,7 +1240,9 @@ method::
     $this->generateUrl('blog_show', array('slug' => 'my-blog-post'), true);
     // http://www.example.com/blog/my-blog-post
 
-From a template, it looks like this:
+From a template, in Twig, simply use the ``url()`` function (which generates an absolute URL) 
+rather than the ``path()`` function (which generates a relative URL). In PHP, pass ``true`` 
+to ``generateUrl()``:
 
 .. configuration-block::