public Settings()
        {
            var dllConfigPath = Assembly.GetExecutingAssembly().GetLocalPath() + ".config";

            var configuration =
                ConfigurationManager.OpenMappedExeConfiguration(
                    new ExeConfigurationFileMap {
                ExeConfigFilename = dllConfigPath
            },
                    ConfigurationUserLevel.None);

            var setting = configuration.AppSettings.Settings["PageSpeedExecutableRelativePath"];
            var pageSpeedExecutableRelativePath = setting == null ||
                                                  setting.Value.IsNullOrWhiteSpace() ||
                                                  LocalHelper.PathHasInvalidChars(setting.Value) ||
                                                  Path.IsPathRooted(setting.Value)
                ? DefaultPageSpeedExecutableRelativePath
                : setting.Value;

            PageSpeedExecutablePath = Path.Combine(
                Path.GetDirectoryName(dllConfigPath).EnsureNotNull(),
                pageSpeedExecutableRelativePath);
        }