`_full_url` breaks URL params in `save`

[gaconnet]

class Fish(ResourceModel):
    token = fields.Field(resource_id=True)

I did this in the console and was pleased:

>>> f = Fish(token='t')
>>> f.save(filet=True)
PUT http://localhost:8000/fish/t/?filet=True

Then I did it this way and was confused:

>>> f = Fish.objects.lookup(token='t')
>>> f.save(filet=True)
PUT http://localhost:8000/fish/t/

Notice how the URL param is gone, as if I passed nothing to save()?

This seems to fix it, but I'd prefer for it to use save kwargs without having to do this:

>>> f = Fish.objects.lookup(token='t')
>>> del f._full_url
>>> f.save(filet=True)
PUT http://localhost:8000/fish/t/?filet=True