Updating site.css compression flag. Should have no problems for backwards compatibility.

src/Makefile

@@ -27,7 +27,7 @@ build:
 	bundle exec lessc --compress ${FA_LESS_MODERN} > ${FA_CSS_MODERN_MIN}
 #	sass ${FA_SCSS_MODERN} ${FA_CSS_MODERN}
 
-	bundle exec lessc --yui-compress ${SITE_LESS} > ${SITE_CSS}
+	bundle exec lessc --compress ${SITE_LESS} > ${SITE_CSS}
 	cp -r ${FA_ROOT_DIRECTORY}/* ../
 	mv README.md-nobuild ../README.md
 	cd assets && mv font-awesome font-awesome-{{ site.fontawesome.version }} && zip -r9 font-awesome-{{ site.fontawesome.version }}.zip font-awesome-{{ site.fontawesome.version }} && mv font-awesome-{{ site.fontawesome.version }} font-awesome