Fixed the way Goutte\Client defined headers are added to Guzzle's req…

…uest object to allow the overwrite of BrowserKit's Client server headers regardless of case.

Goutte/Client.php

@@ -91,10 +91,14 @@ protected function doRequest($request)
         $guzzleRequest = $this->getClient()->createRequest(
             $request->getMethod(),
             $request->getUri(),
-            array_merge($this->headers, $headers),
+            $headers,
             $body
         );
 
+        foreach ($this->headers as $name => $value) {
+            $guzzleRequest->setHeader($name, $value);
+        }
+
         if ($this->auth !== null) {
             $guzzleRequest->setAuth(
                 $this->auth['user'],
@@ -119,8 +123,6 @@ protected function doRequest($request)
             }
         }
 
-        $guzzleRequest->setHeader('User-Agent', $this->server['HTTP_USER_AGENT']);
-
         $guzzleRequest->getCurlOptions()
             ->set(CURLOPT_FOLLOWLOCATION, false)
             ->set(CURLOPT_MAXREDIRS, 0)