Bump zend-stdlib minimum version

Author: Xerkus

composer.json

@@ -24,7 +24,7 @@
         "php": "^5.6 || ^7.0",
         "container-interop/container-interop": "^1.2",
         "psr/container": "^1.0",
-        "zendframework/zend-stdlib": "^3.1"
+        "zendframework/zend-stdlib": "^3.2.1"
     },
     "require-dev": {
         "mikey179/vfsStream": "^1.6.5",