Remove php-di as hard dependency

Author: jaapio

composer.json

@@ -15,13 +15,14 @@
     "api-clients/hydrator": "dev-master",
     "api-clients/service": "dev-master",
     "api-clients/transport": "dev-master",
-    "league/event": "^2.1",
-    "php-di/php-di": "^5.4"
+    "league/event": "^2.1"
   },
   "require-dev": {
-    "api-clients/test-utilities": "^2.0"
+    "api-clients/test-utilities": "^2.0",
+    "php-di/php-di": "^5.4"
   },
   "suggest": {
+    "php-di/php-di": "Use predefined factory to create client",
     "api-clients/resource-generator": "Easy wireframing of resources",
     "wyrihaximus/react-cache-filesystem": "Filesystem cache",
     "wyrihaximus/react-cache-redis": "Redis cache"