Do not allow slash in method name (#33)

* Do not allow / character in method name

* Make StyleCI happy

Author: tuupola

src/CachePlugin.php

@@ -346,7 +346,7 @@ private function configureOptions(OptionsResolver $resolver)
         $resolver->setAllowedValues('hash_algo', hash_algos());
         $resolver->setAllowedValues('methods', function ($value) {
             /* RFC7230 sections 3.1.1 and 3.2.6 except limited to uppercase characters. */
-            $matches = preg_grep('/[^A-Z0-9!#$%&\'*\/+\-.^_`|~]/', $value);
+            $matches = preg_grep('/[^A-Z0-9!#$%&\'*+\-.^_`|~]/', $value);
 
             return empty($matches);
         });