对旧的配置项做兼容
@param  {Config} config
@return {Config}
function adjustOldProperty(config) {
    if (!config.input.cssSource && 'cssRoot' in config.input) {
        config.input.cssSource = config.input.cssRoot;
        delete config.input.cssRoot;
    }
    if (!config.output.cssDist && 'cssRoot' in config.output) {
        config.output.cssDist = config.output.cssRoot;
        delete config.output.cssRoot;
    }
    if (!config.output.imageDist && 'imageRoot' in config.output) {
        config.output.imageDist = config.output.imageRoot;
        delete config.output.imageRoot;
    }
    if (!config.output.maxSingleSize && 'maxSize' in config.output) {
        config.output.maxSingleSize = config.output.maxSize;
        delete config.output.maxSize;
    }
    return config;
}