Laravel - Edit Article only if user is the owner

2015_04_07_204252_create_articles_table.php

<?php
    // database/migrations/2015_04_07_204252_create_articles_table.php


    use Illuminate\Database\Schema\Blueprint;
    use Illuminate\Database\Migrations\Migration;

    class CreateArticlesTable extends Migration
    {
        public function up()
        {
            Schema::create(
                'articles', function ( Blueprint $table )
            {
                $table->increments( 'id' );
                $table->string( 'name' );
                $table->integer( 'user_id' )->unsigned();
                $table->timestamps();

                $table->foreign( 'user_id' )->references( 'id' )->on( 'users' );
            }
            );
        }

        public function down()
        {
            Schema::drop( 'articles' );
        }
    }

Article.php

<?php namespace App;

// app/Article.php

use Illuminate\Database\Eloquent\Model;

class Article extends Model
{
    public function user()
    {
        return $this->belongsTo( 'App\User' );
    }
}

ArticleController.php

<?php namespace App\Http\Controllers;

// app/Http/Controllers/ArticleController.php

use App\Article;
use App\Http\Requests;
use App\Http\Controllers\Controller;

use Illuminate\Http\Request;

class ArticleController extends Controller
{

    public function __construct()
    {
        $this->middleware('auth'); // IMPORTANT!
    }

    public function edit( Requests\ArticleRequest $request, $articles )
    {
        $article = Article::find($articles);

        return view('articles.edit', compact('article'));
    }

    // omitted for brevity
}

ArticleRequest.php

<?php namespace App\Http\Requests;

// app/Http/Requests/ArticleRequest.php

use App\Article;
use App\Http\Requests\Request;

class ArticleRequest extends Request
{
    public function authorize()
    {
        $user    = app( 'auth' )->user();
        $article = Article::findOrFail( $this->articles );  // "articles" is a route parameter

        return $article->user_id === $user->id;
    }

    public function rules()
    {
        return [];
    }

    // optionally override this to redirect back
    public function forbiddenResponse()
    {
        return redirect()->back()->withInput()->withErrors('forbidden');
    }
}

Handler.php

<?php namespace App\Exceptions;

// app\Exceptions\Handler.php

use Exception;
use Illuminate\Database\Eloquent\ModelNotFoundException;// ADD THIS
use Illuminate\Foundation\Exceptions\Handler as ExceptionHandler;

class Handler extends ExceptionHandler
{
    protected $dontReport = [
        'Symfony\Component\HttpKernel\Exception\HttpException'
    ];

    public function report( Exception $e )
    {
        return parent::report( $e );
    }

    public function render( $request, Exception $e )
    {
        // ADD THIS
        if ( $e instanceof ModelNotFoundException )
        {
            return redirect()->back()->withInput()->withErrors( 'model not found' );
        }

        return parent::render( $request, $e );
    }
}

routes.php

<?php
    // app/Http/routes.php

    Route::resource( 'articles', 'ArticleController' );

    Route::get('/', 'WelcomeController@index');

    Route::get('home', 'HomeController@index');

    Route::controllers([
        'auth' => 'Auth\AuthController',
        'password' => 'Auth\PasswordController',
    ]);