[Fix] Make Paginator::getUrl have priority over appends

Currently if for some reason you append a `page` parameter to a Paginator instance, calling `getUrl` with any argument will still return that instead of the requested page :

```php
$sortings = Input::all(); // ['sort' => 'asc', 'page' => 2]
$paginator->appends($sortings);

// Before fix
$paginator->getUrl(3) // ?sort=asc&page=2

// After fix
$paginator->getUrl(3) // ?sort=asc&page=3
```