朴素贝叶斯分类分为两步：
①　　计算特征项和所属类别之间的概率;
②　　判断文本dj是否属于类别ci的概率
本代码为训练阶段(Naive Bayes classification is divided into two steps:
1 Calculate the probability between the feature item and its own category;
2 The probability of judging whether the text dj belongs to the category ci)