README.md in nightcrawler_swift-0.10.0 vs README.md in nightcrawler_swift-0.11.0

@@ -92,9 +92,13 @@
 
 > max_age
 
 Defines the *Cache-Control:max-age=<value>* header.
 
+> expires
+
+Defines the *Expires* header.
+
 > content_encoding
 
 Defines the *Content-Encoding:<vaule>* header
 
 > retries