Redone CSS primarily to make markers and tab button smaller

- Converted to LESS
- Made tab button much smaller so doesn't interfere with content so
much on medium (tablet screen sizes)
- Added brand colour (as variable) used for markers and tab button/line
Changes in JS to reflect CSS changes

- Changed tab width/height in relation to reduced tab border
- Changed breakpoints from 700 to 640
- Added capital 'S' to 'Show note markers'
Tab button images made smaller in line with CSS changes