Update readme

Author: zachborboa

README.md

@@ -187,6 +187,7 @@ Curl::get($url, $data = array())
 Curl::getCookie($key)
 Curl::getOpt($option)
 Curl::getResponseCookie($key)
+Curl::getResponseCookies()
 Curl::head($url, $data = array())
 Curl::headerCallback($ch, $header)
 Curl::options($url, $data = array())