update readme, simplify Usage

Author: johanrosenson

README.md

@@ -17,19 +17,12 @@ composer require devlop/laravel-console-input-validation
 
 ```php
 use Devlop\Laravel\Console\ValidateInput;
-use InvalidArgumentException;
 use Symfony\Component\Console\Input\InputInterface;
-use Webmozart\Assert\Assert; // not required, but used in the example below
 
 class DemoCommand extends Command
 {
     use ValidateInput;
 
-    public function __construct()
-    {
-        parent::__construct();
-    }
-
     /**
      * Validate the console command input.
      *
@@ -39,10 +32,10 @@ class DemoCommand extends Command
     {
         // Example using manual validation
         if (! is_numeric($input->getOption('limit'))) {
-            throw new RuntimeException('--limit must be numeric');
+            throw new InvalidArgumentException('--limit must be numeric');
         }
 
-        // Example using webmozarts/assert:
+        // Example using webmozarts/assert
         Assert::numeric($input->getOption('limit')); // assert that the --limit option got a numeric value
         Assert::greaterThan($input->getOption('limit'), 0); // assert that the --limit option get a value greater than 0
     }