包括如下接口：
- addNewsMedia - 新增图文
- updateNewsInfo - 修改图文

3.5.1 addNewsMedia 添加图文

    WxNewsInfo news1 = new WxNewsInfo();
    news1.setTitle("标题1");
    news1.setThumb_media_id("图片media_id");
    news1.setContent("xxx");
    //....设置图文内容
    WxNewsInfo news2 = new WxNewsInfo();
    news2.setTitle("标题1");
    news2.setThumb_media_id("图片media_id");
    news2.setContent("xxx");
    List<WxNewsInfo> newsList = new ArrayList<>();
    newsList.add(news1);
    newsList.add(news2);
    try {
        String mediaId = iService.addNewsMedia(newsList);
    } catch (WxErrorException e) {
        e.printStackTrace();
    }

3.5.2 updateNewsInfo 修改图文内容

    WxNewsInfo news1 = new WxNewsInfo();
    news1.setTitle("标题1");
    news1.setThumb_media_id("图片media_id");
    news1.setContent("xxx");
    try {
        //参数1：media_id；参数2：图文位置下标。从0开始；参数3：新的图文对象
        WxError result = iService.updateNewsInfo("media_id", 0, news1);
    } catch (WxErrorException e) {
        e.printStackTrace();
    }