use custom class in laravel 5.0

I am using following library for credit card payment:

http://ift.tt/1C5RsbO

i have added code of above library in app\Libraries folder, following is the file i want to include now:

I added following code in my Controller where i want to use this library:

use com\checkout\ApiClient;
$apiClient = new ApiClient('sk_CC937715-4F68-4306-BCBE-640B249A4D50');

But i am getting following error: Please guide.

FatalErrorException in WelcomeController.php line 23: Class 'com\checkout\ApiClient' not found

via Chebli Mohamed