Merge pull request #3 from jkrehm/depend-on-extension

Depend on Zend Opcache extension instead of PHP 5.5

composer.json

@@ -12,7 +12,7 @@
     }
   ],
   "require": {
-    "PHP": ">=5.5.0"
+    "ext-Zend-OPcache": "*"
   }
 }