Fix dependendcy on hierarchical-cache (#149)

* Fix dependendcy on hierarchical-cache

All adapters which use cache/hierarchical-cache use "^0.4", except this void adapter makes it unable to install

* Update composer.json

Author: lunetics

composer.json

@@ -20,7 +20,7 @@
     "require":           {
         "php":                      "^5.6 || ^7.0",
         "psr/cache":                "^1.0",
-        "cache/hierarchical-cache": "^0.3"
+        "cache/hierarchical-cache": "^0.4"
     },
     "require-dev":       {
         "phpunit/phpunit":         "^4.0 || ^5.1",