General layout and UI changes

Not connected to a bounty, sorry. 

Highlights: 
removed navdots (emoji)
added new progress marker (n / steps)
updated icon to flat color
added big icons to challenge page

Didn't yet pull out reset.css.

Logs should be clear though most changes were tweaks.

You'll see a bunch of "add / remove font-awesome" logs. I was trying to add the gem but kept failing. Anyway, I don't think it's necessary anymore.