Feature/directory reader

Now we can fill the this configurations:

```php
 'include'    => ['public',],
    'exclude'    => [
        'directories'   => ['whatever'],
        'files'         => ['README.md', 'LICENSE'],
        'extensions'    => ['.txt'],
        'pattern'       => '404.*'
    ]
```
and run $ php artisan cdn:push

this will print an array of full path of each included file.
similar to configuration, the function naming should follow the command manner. i.e. `$this->directory_manager->read(...)`