phpunit in composer to make @beryllium happy

Author: igorw

composer.json

@@ -12,6 +12,9 @@
     "require": {
         "php": ">=5.4"
     },
+    "require-dev": {
+        "phpunit/phpunit": "~4.2"
+    },
     "autoload": {
         "files": ["src/retry.php"]
     },