Bump laravel ver

Author: lazychaser

README.markdown

@@ -6,7 +6,7 @@
 
 This is a Laravel 4-6 package for working with trees in relational databases.
 
-*   **Laravel 5.7, 5.8, 6.0** is supported since v5
+*   **Laravel 5.7, 5.8, 6.0, 7.0** is supported since v5
 *   **Laravel 5.5, 5.6** is supported since v4.3
 *   **Laravel 5.2, 5.3, 5.4** is supported since v4
 *   **Laravel 5.1** is supported in v3

composer.json

@@ -13,9 +13,9 @@
 
     "require": {
         "php": ">=7.1.3",
-        "illuminate/support": "~5.7.0|~5.8.0|~6.0",
-        "illuminate/database": "~5.7.0|~5.8.0|~6.0",
-        "illuminate/events": "~5.7.0|~5.8.0|~6.0"
+        "illuminate/support": "~5.7.0|~5.8.0|~6.0|~7.0",
+        "illuminate/database": "~5.7.0|~5.8.0|~6.0|~7.0",
+        "illuminate/events": "~5.7.0|~5.8.0|~6.0|~7.0"
     },
 
     "autoload": {