Validation rules won't work until manual loading the provider once

[ametad]

Hi @antonioribeiro ,

Thank you for your work on this package.
I have a question on the validation rules that I don't seem to get working. It looks like the validation rules are not yet loaded before you load app('pragmarx.countries'); explicitly. After that the validation does work correctly.

Version "pragmarx/countries-laravel" === '0.6.3'

Example steps to reproduce the error

class PostController extends Controller

    public function store(Request $request)
    {
        // Without this the 'cca2' validation rule gives error. Please toggle on/off.
        $foo = app('pragmarx.countries');

        $validated = $this->validate($request, [
           'country_code' => 'nullable|string|size:2|cca2',
        ];

        dd($validated);
    }

The error I get when the rule is not loaded:

Method Illuminate\Validation\Validator::validateCca2 does not exist.

Perhaps this has something to do with the defered state in \PragmaRX\CountriesLaravel\Package\ServiceProvider ?

[ametad]

I guess this is a problem for some time now, according to #14