Fix version

Author: jeckel

composer.json

@@ -23,7 +23,7 @@
     "php": "^7.2",
     "psr/event-dispatcher": "^1.0",
     "psr/container": "^1.0",
-    "jeckel-lab/contract": "dev-master"
+    "jeckel-lab/contract": "0.1"
   },
   "require-dev": {
     "phpunit/phpunit": "^8.4",