Fixed build for ruby 1.8
Fixed build for ruby 1.8

See #121

rubixware/font-awesome-rails,bokmann/font-awesome-rails,wwidea/font-awesome-rails,bokmann/font-awesome-rails,estebaninformatica/font-awesome-rails,bokmann/font-awesome-rails,rubixware/font-awesome-rails,wwidea/font-awesome-rails,estebaninformatica/font-awesome-rails