Move phpunit dependency to dev.

Author: Crell

composer.json

@@ -1,20 +1,22 @@
 {
-  "name": "platformsh/config-reader",
-  "description": "Small helper to access Platform.sh environment variables",
-  "license": "MIT",
-  "authors": [
-    {
-      "name": "Ori Pekelman",
-      "email": "ori+github@pekelman.com"
+    "name": "platformsh/config-reader",
+    "description": "Small helper to access Platform.sh environment variables",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Ori Pekelman",
+            "email": "ori+github@pekelman.com"
+        },
+        {
+            "name": "Patrick Dawkins"
+        }
+    ],
+    "require": {
+        "php": ">=7.1"
+    },
+    "require-dev": {
+        "phpunit/phpunit": "^7.5"
     },
-    {
-      "name": "Patrick Dawkins"
-    }
-  ],
-  "require": {
-    "php": ">=7.1",
-    "phpunit/phpunit": "^7.5"
-  },
     "autoload": {
         "psr-4": {
             "Platformsh\\ConfigReader\\": "src"
@@ -25,9 +27,9 @@
             "Platformsh\\ConfigReader\\": "tests"
         }
     },
-  "config": {
-    "platform": {
-      "php": "7.1"
+    "config": {
+        "platform": {
+            "php": "7.1"
+        }
     }
-  }
 }