Fix bogue when adding a new formset with horizontal=True

[erozqba]

This fixes a bug when adding new formset (that use horizontal=True) using javascript (when you click the link add another...) after the page is loaded.

To verify the bug:

1. Install this branch locally and remove the modifications I have made in the file smart_selects/static/smart-selects/admin/js/bindfields.js
2. Go to http://127.0.0.1:8000/admin/test_app/person/ and add at least two persons
3. Go to http://127.0.0.1:8000/admin/test_app/talent/ and add at least two talents and select differents persons that have the talent you are adding.
4. Go to http://127.0.0.1:8000/admin/test_app/group/add/ for adding a group, here try to add more than one person with talent in the membership, the current loaded inline should work as expected, but when you add a new inline using the link Add another Membership the new ones should not work as expected.

The steps to verify the fix are:

1. Apply the changes I have made in the smart_selects/static/smart-selects/admin/js/bindfields.js

Ref: issue #210

[coveralls]

Coverage increased (+0.9%) to 89.565% when pulling 10687cc68818f7484c88b6f10b80b45fc7493b1e on erozqba:adding_formset_horizontal_true into ae906b95d3f8e770a7d84ee59ff53ebb1e53b883 on digi604:master.

[blag]

Thanks!