func (*uglifyjs) IsInstalled() bool { return computil.CmdAvailable(exec.Command(uglify_CMD, "-V")) }
func (*coffeec) IsInstalled() bool { return computil.CmdAvailable(exec.Command(coffee_CMD, "-v")) && computil.CmdAvailable(exec.Command(uglify_CMD, "-V")) }
func (*lessc) IsInstalled() bool { return computil.CmdAvailable(exec.Command(less_CMD, "-v")) }