Reference states.js exactly

Fixes issue where in production the route may be:

<script src=//myappname-spree-staging-assets.s3.amazonaws.com/states.js type=text/javascript></script>
<script src=//myappname-spree-staging-assets.s3.amazonaws.com/assets/admin/address_states-444635bf9f1506dc0f644eec388b4e4b.js type=text/javascript></script>