Sort packages (#313)

This reduces conflict risks and naturally groups packages by vendor.

composer.json

@@ -17,32 +17,35 @@
     ],
     "require": {
         "php": "^5.3 || ^7.0",
-        "symfony/http-foundation": "^2.3 || ^3.0",
-        "symfony/form": "^2.3 || ^3.0",
+        "cocur/slugify": "^1.4 || ^2.0",
         "symfony/config": "^2.3 || ^3.0",
+        "symfony/form": "^2.3 || ^3.0",
+        "symfony/http-foundation": "^2.3 || ^3.0",
+        "symfony/property-access": "^2.3 || ^3.0",
         "symfony/translation": "^2.3 || ^3.0",
         "symfony/validator": "^2.3 || ^3.0",
-        "symfony/property-access": "^2.3 || ^3.0",
-        "twig/twig": "^1.23",
-        "cocur/slugify": "^1.4 || ^2.0"
+        "twig/twig": "^1.23"
     },
     "require-dev": {
-        "matthiasnoback/symfony-config-test": "^0.4 || ^1.0",
-        "matthiasnoback/symfony-dependency-injection-test": "^0.7",
         "doctrine/orm": "^2.4",
         "doctrine/phpcr-odm": "^1.0",
-        "jackalope/jackalope-doctrine-dbal": "^1.0",
         "friendsofsymfony/rest-bundle": "^1.1 || ^2.0",
+        "jackalope/jackalope-doctrine-dbal": "^1.0",
         "jms/serializer-bundle": "0.11 - 0.13 || ^1.0",
+        "matthiasnoback/symfony-config-test": "^0.4 || ^1.0",
+        "matthiasnoback/symfony-dependency-injection-test": "^0.7",
+        "nelmio/api-doc-bundle": "^2.11",
         "sensio/framework-extra-bundle": "^2.3 || ^3.0",
-        "sonata-project/exporter": "^1.3",
-        "symfony/phpunit-bridge": "^2.7",
         "sllh/php-cs-fixer-styleci-bridge": "^2.0",
-        "nelmio/api-doc-bundle": "^2.11"
+        "sonata-project/exporter": "^1.3",
+        "symfony/phpunit-bridge": "^2.7"
     },
     "autoload": {
         "psr-4": { "Sonata\\CoreBundle\\": "" }
     },
+    "config": {
+        "sort-packages": true
+    },
     "extra": {
         "branch-alias": {
             "dev-master": "3.x-dev"