update composer

composer.json

@@ -11,14 +11,14 @@
         }
     ],
     "require": {
-        "php": ">=5.4",
+        "php": ">=5.6",
         "symfony/serializer": "~2.7|~3.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.4|^5.6",
         "squizlabs/php_codesniffer": "~2.0",
         "satooshi/php-coveralls": "~1.0",
-        "elasticsearch/elasticsearch": "~2.0"
+        "elasticsearch/elasticsearch": "~5.0"
     },
     "autoload": {
         "psr-4": {