FortAwesome/Font-Awesome — pull request #3022 by ScottHamper (2014-03-05 17:00:38+00:00)
Title: SASS will now properly substitute variables in DXImageTransform values.

SASS doesn't appear to substitute variables in DXImageTransform values normally. This also caused an issue when trying to minify the compiled CSS file, as the file did not have fully valid CSS.

Updating the DXImageTransform values to use SASS interpolation appears to resolve the issue.