Bump to L5.5 minimum

Author: arrilot

README.md

@@ -11,9 +11,6 @@
 
 1) Run ```composer require arrilot/laravel-widgets```
 
-For Laravel >= 5.5 that's all.
-For Laravel < 5.5 read on.
-
 2) Register a service provider in the `app.php` configuration file
 
 ```php