Annotate method hints for Laravel IDE helper

[georgms]

By annotating method hints PHPStorm (and other IDEs) will be available to autocomplete the methods provided by the facade. The change should just be:

<?php namespace Huddle\Zendesk\Facades;

use Illuminate\Support\Facades\Facade;

/**
 * @mixin \Zendesk\API\HttpClient
 */
class Zendesk extends Facade {
    …
}

Laravel IDE helper will be able to extract this annotation and provide IDE autocompletion.