Patch simple cache (#131)

* Added test and fixed minor bug

* Added meta files

* Added class comment

* Updated integration test version

* Require Symfony for testing

* Require mockery

Author: Nyholm

composer.json

@@ -31,7 +31,7 @@
     },
     "require-dev":       {
         "phpunit/phpunit":         "^4.0 || ^5.1",
-        "cache/integration-tests": "^0.13"
+        "cache/integration-tests": "^0.14"
     },
     "provide":           {
         "psr/cache-implementation": "^1.0"