I was opening an issue about CSS class namespacing when I found an already closed one. So I realized I had just downloaded a very outdated version of your icons from your personal website. The download link of that outdated package is:
https://github.com/downloads/somerandomdude/Iconic/iconic.zip
Consider updating that package or, better, you can link directly to the one served by GitHub, which will be always up-to-date:
https://github.com/somerandomdude/Iconic/archive/master.zip