Added Turbolink support for the checkout forms. Turbolink was conflicting with the JS in the copy_from_billing functionality and some other JS activity within the checkout process.
Added Turbolink exception to Proceed to Checkout button, as one solution attempt.
Merge pull request #62 from marcamillion/b05d87e80198326da6a13222c2b9fb277835fb6d

Completed Turbolink compatibility