说明：  神经网络比较基础的算法，实现梯度下降和反向传播，以及L2规范化、交叉熵代价函数的引入，卷积神经网络 该算法用于mnist数据测试，有详细中文注释
(Neural network based on the comparison algorithm, gradient descent and back-propagation, and L2 standardization introduced cross entropy cost function, convolution neural network algorithm for mnist test data, a detailed Chinese Notes)