Issue 1788

Fixes #1788 

@arkon The problem was that now the codeviewer div is scrolling vertically, rather than the image_container (like what it was before). I couldn't figure out how to change that back, so I did this instead.

Ideally, we'd fix this; the problem is that now the horizontal scrollbar doesn't appear until you scroll down to the very bottom.

However, I believe that fixing this issue for current courses takes priority.