Laravel / Intervention Image Class - class not found

I just installed Intervention Image Class following instructions from here: http://image.intervention.io/getting_started/installation

I also added these 2 lines into config/app.php file:

'Intervention\Image\ImageServiceProvider'

'Image' => 'Intervention\Image\Facades\Image'

When I open my website, i get this error:

Class 'Intervention\Image\ImageServiceProvider' not found

Why is that and what should I do now?

Step 1:

Add "intervention/image": "dev-master" to the “require” section of your composer.json file.

"require": {
    "laravel/framework": "4.1.*",
    "intervention/image": "dev-master"
},

Step 2:

Run CMD;
$ composer install

If you've got this warning:

Warning: The lock file is not up to date with the latest changes in composer.json. You may be getting outdated dependencies. Run update to update them.

do $ composer update and then $ composer install

Step 3:

open the config/app.php file. Add this to the $providers array.

Intervention\Image\ImageServiceProvider::class

Step 4:

Next add this to the $aliases array.

'Image' => Intervention\Image\Facades\Image::class

Step 5:

If there is an error;

Class 'Intervention\Image\ImageServiceProvider' not found

try

$ composer update