Fix installation on new versions of Laravel 6.0

Author: AlexLove77

composer.json

@@ -1,7 +1,7 @@
 {
   "name": "elasticquent/elasticquent",
   "type": "library",
-  "description": "Maps Laravel Eloquent models to Elasticsearch types.",
+  "description": "Maps Laravel Eloquent models to Elasticsearch types. (Laravel 6)",
   "keywords": [
     "elasticsearch",
     "eloquent",
@@ -18,8 +18,8 @@
   ],
   "require": {
     "php": ">=5.4.0",
-    "illuminate/database": "~4.2|^5",
-    "illuminate/config": "~4.2|^5",
+    "illuminate/database": "~4.2|^5|^6",
+    "illuminate/config": "~4.2|^5|^6",
     "nesbot/carbon": "~1.0|~2",
     "elasticsearch/elasticsearch": "~6.1"
   },