bug #4494 Updated the Symfony Installer installation instructions (javiereguiluz)

This PR was squashed before being merged into the 2.3 branch (closes #4494).

Discussion
----------

Updated the Symfony Installer installation instructions

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

@weaverryan @wouterj @xabbuh I'm truly sorry for *pushing* you, but this is a **ultra-high priority PR** because the current Symfony installation instructions displayed on http://symfony.com/doc/current/quick_tour/the_big_picture.html are broken.

Commits
-------

f374bf4 Updated the Symfony Installer installation instructions

Author: wouterj

quick_tour/the_big_picture.rst

@@ -31,7 +31,7 @@ On **Linux** and **Mac OS X** systems, execute the following console commands:
 
 .. code-block:: bash
 
-    $ curl -sS https://symfony.com/installer | php
+    $ curl -LsS http://symfony.com/installer > symfony.phar
     $ sudo mv symfony.phar /usr/local/bin/symfony
 
 .. note::
@@ -41,7 +41,7 @@ On **Linux** and **Mac OS X** systems, execute the following console commands:
 
     .. code-block:: bash
 
-        $ php -r "readfile('https://symfony.com/installer');" | php
+        $ php -r "readfile('http://symfony.com/installer');" > symfony.phar
         $ sudo mv symfony.phar /usr/local/bin/symfony
 
 After installing the Symfony installer, you'll have to open a new console window
@@ -53,9 +53,9 @@ to be able to execute the new ``symfony`` command:
 
 On **Windows** systems, execute the following console command:
 
- .. code-block:: bash
+.. code-block:: bash
 
-    c:\> php -r "readfile('https://symfony.com/installer');" | php
+    c:\> php -r "readfile('http://symfony.com/installer');" > symfony.phar
 
 This command downloads a file called ``symfony.phar`` which contains the Symfony
 installer. Save or move that file to the directory where you create the Symfony