Bump ElasticSearch version to ~6.0 (#159)

* Removed invalid 'fields' parameter
* Bumped ElasticSearch version to ~6.0
Thanks @coffeeburrito!

composer.json

@@ -21,7 +21,7 @@
     "illuminate/database": "~4.2|^5",
     "illuminate/config": "~4.2|^5",
     "nesbot/carbon": "~1.0",
-    "elasticsearch/elasticsearch": ">1.0 <2.2"
+    "elasticsearch/elasticsearch": "~6.0"
   },
   "require-dev": {
     "phpunit/phpunit": "~4.2|~5.0",

src/ElasticquentTrait.php

@@ -225,7 +225,7 @@ public static function searchByQuery($query = null, $aggregations = null, $sourc
     {
         $instance = new static;
 
-        $params = $instance->getBasicEsParams(true, true, true, $limit, $offset);
+        $params = $instance->getBasicEsParams(true, $limit, $offset);
 
         if (!empty($sourceFields)) {
             $params['body']['_source']['include'] = $sourceFields;
@@ -366,7 +366,7 @@ public function getIndexedDocument()
      *
      * @return array
      */
-    public function getBasicEsParams($getIdIfPossible = true, $getSourceIfPossible = false, $getTimestampIfPossible = false, $limit = null, $offset = null)
+    public function getBasicEsParams($getIdIfPossible = true, $limit = null, $offset = null)
     {
         $params = array(
             'index' => $this->getIndexName(),
@@ -377,11 +377,6 @@ public function getBasicEsParams($getIdIfPossible = true, $getSourceIfPossible =
             $params['id'] = $this->getKey();
         }
 
-        $fields = $this->buildFieldsParameter($getSourceIfPossible, $getTimestampIfPossible);
-        if (!empty($fields)) {
-            $params['fields'] = implode(',', $fields);
-        }
-
         if (is_numeric($limit)) {
             $params['size'] = $limit;
         }