Fix backbone remaining items counter

This reverts commit 9d4b0b064efbcf187552b381c61c9185773ce80c.

The simplified function call changes the semantics of it. The signature of
without is: _.without(array, [*values]), which is why apply must be used here.
Merge pull request #370 from passy/backbone-remaining-fix

Backbone remaining items counter does not update. Reverts 9d4b0b064efbcf187552b381c61c9185773ce80c