Fix indentation

Author: Márk Sági-Kazár

clients/includes/install-message-factory.inc

@@ -3,7 +3,7 @@ to install one as well (for example `Guzzle PSR-7`_):
 
 .. code-block:: bash
 
-$ composer require guzzlehttp/psr7
+    $ composer require guzzlehttp/psr7
 
 In order to provide full interoperability, message implementations are
 accessed through :ref:`factories <message-factory>`. Message factories for
@@ -12,7 +12,7 @@ accessed through :ref:`factories <message-factory>`. Message factories for
 
 .. code-block:: bash
 
-$ composer require php-http/message
+    $ composer require php-http/message
 
 .. _Diactoros: http://docs.guzzlephp.org/en/5.3/
 .. _Guzzle PSR-7: https://github.com/guzzle/psr7