Merge pull request #270 from kreischweide/master

[Book][Cache] Corrected variable

Author: weaverryan

book/http_cache.rst

@@ -643,7 +643,7 @@ exposing a simple and efficient pattern::
  $response->setLastModified($article->getPublishedAt());
 
  // Check that the Response is not modified for the given Request
- if ($response->isNotModified($request)) {
+ if ($response->isNotModified($this->get('request'))) {
  // return the 304 Response immediately
  return $response;
  } else {