deprecate debug_plugin options (#64)

Author: fbourigault

CHANGELOG.md

@@ -6,6 +6,12 @@
 
 - `QueryDefaultsPlugin` to add default query parameters. 
 
+## Unreleased
+
+### Deprecated
+
+- The `debug_plugins` option for `PluginClient` is deprecated and will be removed in 2.0. Use the decorator design pattern instead like in [ProfilePlugin](https://github.com/php-http/HttplugBundle/blob/de33f9c14252f22093a5ec7d84f17535ab31a384/Collector/ProfilePlugin.php).
+
 ## 1.4.2 - 2017-03-18
 
 ### Deprecated

src/PluginClient.php

@@ -108,6 +108,10 @@ public function sendAsyncRequest(RequestInterface $request)
      */
     private function configure(array $options = [])
     {
+        if (isset($options['debug_plugins'])) {
+            @trigger_error('The "debug_plugins" option is deprecated since 1.5 and will be removed in 2.0.', E_USER_DEPRECATED);
+        }
+
         $resolver = new OptionsResolver();
         $resolver->setDefaults([
             'max_restarts' => 10,