added get enpoint

Author: npetrunova

src/Api/Fields.php

@@ -8,4 +8,11 @@ class Fields extends ApiAbstract {
 
     protected $endpoint = 'fields';
 
+    public function getAccountFields() {
+
+        $response = $this->restClient->get($this->endpoint);
+
+        return $response['body'];
+    }
+
 }