Associations code should be able handle multiple word classes

Currently the model name is not converted yet from snake_case to CamelCase:

```
$ learn rails car has_many :door_handles
# def door_handles
#   Door_handle.where(car_id: self.id)
# end
```

This is what the output should be:

```
$ learn rails car has_many :door_handles
# def door_handles
#   DoorHandle.where(car_id: self.id)
# end
```