Fix Definition#name to convert @options[:as] to string
Fix Definition#name to convert @options[:as] to string

In case define property with `as` and `selectable`
options:

```
property :first_name, as: :name, selectable: true
```

Representer#handle_definition? returns false
because `@options[:as]` is a Symbol and selector keeps
their keys as String.

luvtechno/garage,takashi/garage,cookpad/garage,cookpad/garage,takashi/garage,kenchan0130/garage,taiki45/garage,taiki45/garage,y-yagi/garage,kenchan0130/garage,kenchan0130/garage,cookpad/garage,luvtechno/garage,cookpad/garage,luvtechno/garage,y-yagi/garage,takashi/garage,y-yagi/garage,taiki45/garage