Review updates, and lots of 'em:

- Fix up IE conditional comments
- Improve image/CSS/markup for FxOS logo
- Hide next/prev/close buttons when on home/intro screen
- Focus next button after clicking a phone icon (instead of leaving
  focus on phone icon)
- Add tabindex to headings for responsive/IE
- Fix Safari issue with blue background animation
- Update photo credit link color for IE
- Add tests for mozilla-pager.js
- Remove unused font-face
- Improve phone icon/list markup

For mozilla-pager.js:

- Add afterPageChanged callback to instantiation options param