CSS comments
Move some common code from curriculum → library
Move some common code from curriculum → library
.topic style fixes for border and icons

* Remove the border from the .topic which makes the main CSS
  unnecessary (it's been removed)
* Make sure the icons for each item in a topic file are contained to
  only 1 line height (1em)
* improve the selector of the background to be tigher
  " " → ">"
CSS improvements to topics