Range with nullable 

Version: 1.0.2

```php
'limit' => Expect::int(null)->min(1)->nullable(),
```

When limit is null, exception throwed "The option 'limit' expects to be int or null in range 1.., null given."

Dump of variable $expected:
```php
int|null:1..
```

expected:
```php
int:1..|null
```

then everything is fine