First pass of new header
Better drop down targets and new button style
Zoom cursors on images
Only show zoom-in cursor when zoomed-out
New markdown styles and document icons
Error styles, uploading styles
Sticky header, fixed touch events, retina progress bar
Don't use serif type for markdown
Tweak Markdown styles

- tighter spacing
- no bottom border on H2
- no bold on headings
Merge branch 'hector'

Mostly style changes
Update emoji
Move quote styles from inline to CSS file