allow to use elasticsearch 5 or 6

Author: Simonas Šerlinskas

composer.json

@@ -21,10 +21,11 @@
         "doctrine/cache": "~1.4",
         "doctrine/collections": "~1.4",
         "monolog/monolog": "~1.10",
-        "ongr/elasticsearch-dsl": "~5.0"
+        "ongr/elasticsearch-dsl": "~5.0|~6.0"
     },
     "require-dev": {
-        "mikey179/vfsStream": "~1.4",
+        "elasticsearch/elasticsearch": "~5.0|~6.0",
+        "mikey179/vfsstream": "~1.4",
         "phpunit/phpunit": "~5.6",
         "squizlabs/php_codesniffer": "~2.0",
         "satooshi/php-coveralls": "~1.0",
@@ -45,7 +46,7 @@
     "minimum-stability": "dev",
     "extra": {
         "branch-alias": {
-            "dev-master": "5.1-dev"
+            "dev-master": "5.2-dev"
         }
     }
 }