Missing bootstrap form classes on state and country select

[adamakhtar]

On the 3-0stable branch it seems only the country and state select boxes are missing .form-control classes which are required by bootstrap.

I don't know if this is intentional as I'm new to both Spree and this extension.

I forked the repo and made tiny adjustments and both the selects render correctly.

My adjustments can be seen here: https://github.com/robodisco/spree_address_book/commit/095166f7569daffc140427ca1007b2ea62103156

If you like I can merge this into 3-0stable and make a pull request.