Fix styling on mailing list subscription page

Mailing List Subscription Page:
  -Input and Select box are shortened and now tied to Foundation responsive grid.
  -Added custom styling to input field and select box

Looks like client side validation is turned off for this form, so if the email field is left blank it takes you to a new form on the mailchimp site.  I left it alone, not sure if there is a separate issue for this, or if that's how you want to keep it.
Hey, @jjidt - thanks so much for this PR! It looks like you have a little switch-up in the nesting here for the closing `<select>` and `<div>` tags.

That said, I've already deployed this to staging and it looks great! Once you make that little change, it should be ready to go into production. :+1: :confetti_ball: