ECOM-811 design and layout changes

@wedaly @stephensanchez @rlucioni here are the style and text updates. Unfortunately I had to use teh dreaded !important in my Sass to override some ridiculously specific selectors, but after the A/B test we can clean this up by removing the legacy styles.
A few things on this line. First, it's not marked for translation. Second, should the "(x)" be replaced with something? Finally, this copy reads "register" where it should really read "enroll"; we should talk to Griff about this and the other line of copy which uses "register" instead of "enroll."