Merge branch '5.6' into 5.7

Merge pull request LaravelCollective#567 from yajra/patch-57

Add support for Laravel 5.7

Allow sub-select to be iterable to accept array and collection (Larav…

…elCollective#540)

Can set class attribute in array. (LaravelCollective#521)

In case of you want to add class by condition.

```
Form::text('name', null, ['class' => [
    'form-control-,
    $error ? 'is-invalid' : '',
]]);
```

Add range, month, week. (LaravelCollective#520)

* Added range, month, week.

* Added URL test.

* Removed duplicate function testFormFile.

Update to PHPUnit 7.1 (LaravelCollective#511)

Fix the issue where defaults has a higher priority then the attributes (

LaravelCollective#509)

Update composer.json

Placeholder for select element not hidden anymore (LaravelCollective#493

) (LaravelCollective#499)

* Placeholder for select element not hidden anymore (LaravelCollective#493)

* Fix tests for placeholder select element without hidden attribue

Placeholder for select element not hidden anymore (LaravelCollective#493

) (LaravelCollective#499)

* Placeholder for select element not hidden anymore (LaravelCollective#493)

* Fix tests for placeholder select element without hidden attribue