Allow passing just a boolean as the arg options

Right now, we have a huge amount of repeated code that looks like:
```php
'x' => array(
    'required' => true,
),
'y' => array(
    'required' => false,
),
```

We can remove this boilerplate while still allowing the extensibility of different options for those who want to use it. This PR changes the code to allow passing just a boolean if you're doing the simple stuff.
```php
'x' => true,
'y' => false,
```