画一个数字，查看CNN如何预测它
http://scs.ryerson.ca/~aharley/vis/conv/flat.html
2D Visualization of a Convolutional Neural Network
Fully-connected layer 2,unit 97
Fully-connected layer 1,unit 119
Downsampling layer 2,filter 4,unit 17
Convolution layer 2,filter 6,unit 54
Downsampling layer 1,filter 2,unit 120
Convolution layer 1,filter 2,unit 100
Input layer,unit 245
