Header, responsiveness, code clean

Header, responsiveness, code clean

- Implementing & styling top-links dropdown (finished)
- Adjusting/fixing responsive display - top nav is now fully
  responsive
- Adjusting page margin offsets in interior pages given the
  different header height
- Greatly reducing header height in mobile, fitting in image and
  search
- Adjust header hover styles and search width
- Adjusting fixed-header styles
- Fixing some site colors using the wrong $blue code
- Cleaning up irrelevant code comments