improve plugin configuration example (#234)

splitting up the examples for plugin configuration to make it easier to see what you can do

Author: dbu

integrations/symfony-bundle.rst

@@ -224,35 +224,26 @@ services are:
 Plugins
 ```````
 
-Clients can have plugins. Generic plugins from ``php-http/plugins`` (e.g. retry
-or redirect) can be configured globally. You can tell the client which of those
-plugins to use, as well as custom plugins that you configured a service for.
+Clients can have plugins that act on the request before it is sent out and/or
+on the response before it is returned to the caller. Generic plugins from 
+``php-http/client-common`` (e.g. retry or redirect) can be configured globally.
+You can tell the client which of those plugins to use, as well as specify the
+service names of custom plugins that you want to use.
 
 Additionally you can configure any of the ``php-http/plugins`` specifically on
 a client. For some plugins this is the only place where they can be configured.
 The order in which you specify the plugins **does** matter.
 
-.. code-block:: yaml
-
-    // services.yml
-    acme_plugin:
-        class: Acme\Plugin\MyCustomPlugin
-        arguments: ["%some_parameter%"]
+Configure plugins directly on the client:
 
 .. code-block:: yaml
 
     // config.yml
     httplug:
-        plugins:
-            cache:
-                cache_pool: 'my_cache_pool'
         clients:
             acme:
                 factory: 'httplug.factory.guzzle6'
                 plugins:
-                    - 'acme_plugin'
-                    - 'httplug.plugin.cache'
-                    - 'httplug.plugin.retry'
                     - add_host:
                         host: "http://localhost:8000"
                     - header_defaults:
@@ -265,6 +256,40 @@ The order in which you specify the plugins **does** matter.
                             password: 'p4ssw0rd'
 
 
+Configure the cache plugin globally and use it in the ``acme`` client:
+
+.. code-block:: yaml
+
+    // config.yml
+    httplug:
+        plugins:
+            cache:
+                cache_pool: 'my_cache_pool'
+        clients:
+            acme:
+                factory: 'httplug.factory.guzzle6'
+                plugins:
+                    - 'httplug.plugin.cache'
+
+Configure a service for your custom plugin and use it in the client:
+
+.. code-block:: yaml
+
+    // services.yml
+    acme_plugin:
+        class: Acme\Plugin\MyCustomPlugin
+        arguments: ["%some_parameter%"]
+
+.. code-block:: yaml
+
+    // config.yml
+    httplug:
+        clients:
+            acme:
+                factory: 'httplug.factory.guzzle6'
+                plugins:
+                    - 'acme_plugin'
+
 Authentication
 ``````````````