参考博客：http://blog.csdn.net/juewu1993/article/details/54773269
http://blog.csdn.net/samylee/article/details/51201744
http://blog.csdn.net/sinat_30071459/article/details/50723212
http://blog.csdn.net/zhangjunbob/article/details/52769381 这个博客对pascal voc数据集进行了分析讲解