CSS Refactoring vanilla-style

@kevinsproles @hippee-lee

### CSS Changes since Friday evening

- Large Add-to-Cart Button
- Add product features, techInfo and extendedInfo
- Added ShareThis sharing icons -needs work (there is JS and CSS in HTML)
  - need to figure out if we want to customize JS for this plug-in
- Fix footer hr line extending too wide
- Delete unused stylesheets
- Refactor class names to be more semantic
- Added styles to mobile-xs view for product tiles