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.
You should use `nextStepName` here instead, since the step numbers / names can change.  If we need to change the name text, we need to do so on the Python side.