The octicon font by github (https://github.com/styleguide/css/7.0) provides some nice icons embedded in a font. This package provides an easier access to them and must be used with the relevant face (octicons).
I do not provide the octicon font. You will need to install it yourself from the github styleguide site (search in the page source).
For more details on these features, see github page: https://github.com/rougier/emacs-octicons