Remove php-di as hard dependency

Author: jaapio

composer.json

@@ -14,7 +14,6 @@
     "api-clients/hydrator": "^1.0.1",
     "api-clients/middleware": "^4.0 || ^3.0 || ^2.0 || ^1.1",
     "api-clients/transport": "^3.0 || ^2.0 || ^1.0",
-    "php-di/php-di": "^5.4.3",
     "psr/container": "^1.0"
   },
   "require-dev": {