Issue with mapping configuration

[yndlingsfar]

There is an issue in /LaravelSerializer/MetadataDriver.php, the configuration from the Readme is not working anymore. e.g. the given configuration

'attributes' => [ 'firstName' ]

fails because in line 82 of MetaDriver.php this is interpreted as $attribute = 0; $attributeConfig = 'firstname';

And because of that $class->hasProperty($attribute) returns false (of course)