I18n ajax cart

- Reverted layout to use divs and CSS table styles instead of native tables
  - Could not animate height of table rows, so ajax cart appeared _janky_
- Updated ajaxify.js to include strings and `NaN` string fix

#### Other fixes
- Re-included checkout fixes (some buttons were transparent)
- Include ajaxify cart CSS before Timber so it can be overridden

cc/ @stevebosworth @mpiotrowicz