CSS and layout update

I had a steps marked in the topbar, which was looking pretty cool and was indicating the linear direction towards which the course should be taken, but then I thought up of different way of indication which module is previous and/or next in the sidebar, which I think is a bit cooler. 
I had only commented this out, in case you would think that indication of previous/next module is not appropriate, to give you this option. I intend to take this out and clean things up on the next pull request.
The comment tag works the same as Django comment tag, it does not render anything between them :)