Define the platform in the composer.json

Fix #543

composer.json

@@ -35,5 +35,10 @@
         "defuse/php-encryption": "^2.1",
         "react/child-process": "^0.5.0",
         "clue/buzz-react": "^2.1"
+    },
+    "config": {
+        "platform": {
+            "php": "5.6"
+        }
     }
 }

composer.lock

@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "content-hash": "4bc9f0d1a2b43d1e486efd8599d7ff32",
+    "content-hash": "362fec1aa6ec47cb436b6355a78f0d9d",
     "packages": [
         {
             "name": "cboden/ratchet",
@@ -408,25 +408,30 @@
         },
         {
             "name": "evenement/evenement",
-            "version": "v3.0.1",
+            "version": "v2.1.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/igorw/evenement.git",
-                "reference": "531bfb9d15f8aa57454f5f0285b18bec903b8fb7"
+                "reference": "6ba9a777870ab49f417e703229d53931ed40fd7a"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/igorw/evenement/zipball/531bfb9d15f8aa57454f5f0285b18bec903b8fb7",
-                "reference": "531bfb9d15f8aa57454f5f0285b18bec903b8fb7",
+                "url": "https://api.github.com/repos/igorw/evenement/zipball/6ba9a777870ab49f417e703229d53931ed40fd7a",
+                "reference": "6ba9a777870ab49f417e703229d53931ed40fd7a",
                 "shasum": ""
             },
             "require": {
-                "php": ">=7.0"
+                "php": ">=5.4.0"
             },
             "require-dev": {
-                "phpunit/phpunit": "^6.0"
+                "phpunit/phpunit": "^6.0||^5.7||^4.8.35"
             },
             "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.0-dev"
+                }
+            },
             "autoload": {
                 "psr-0": {
                     "Evenement": "src"
@@ -447,7 +452,7 @@
                 "event-dispatcher",
                 "event-emitter"
             ],
-            "time": "2017-07-23T21:35:13+00:00"
+            "time": "2017-07-17T17:39:19+00:00"
         },
         {
             "name": "ezyang/htmlpurifier",
@@ -2293,5 +2298,8 @@
         "ext-mbstring": "*",
         "ext-imagick": "*"
     },
-    "platform-dev": []
+    "platform-dev": [],
+    "platform-overrides": {
+        "php": "5.6"
+    }
 }