Add system requirements.

Author: yajra

readme.md

@@ -39,6 +39,10 @@ This package is created to handle [server-side](https://www.datatables.net/manua
         - Built-in support for exporting to CSV, EXCEL and PDF using [Laravel-Excel](https://github.com/Maatwebsite/Laravel-Excel).
         - Built-in printer friendly view or create your own by overriding `printPreview()` method.
 
+## Requirements:
+    - PHP 5.5.9 or later.
+    - Laravel 5.0 and later.
+
 ## Laravel 4.2 & DataTables v1.9.x Users
 Most of the latest updates/features are not available on these versions. Please check [L4 Branch](https://github.com/yajra/laravel-datatables/tree/L4) and [L5 DT1.9](https://github.com/yajra/laravel-datatables/tree/L5-DT1.9) for old documentations of its features.