[docs] fix pooling markdown and add some comments in tutorial
[docs] fix pooling markdown and add some comments in tutorial

gnina/gnina,gogartom/caffe-textmaps,CZCV/s-dilation-caffe,wangg12/caffe,tackgeun/caffe,wangg12/caffe,longjon/caffe,gogartom/caffe-textmaps,longjon/caffe,CZCV/s-dilation-caffe,gnina/gnina,tackgeun/caffe,longjon/caffe,gnina/gnina,tackgeun/caffe,gnina/gnina,tackgeun/caffe,gogartom/caffe-textmaps,wangg12/caffe,gnina/gnina,wangg12/caffe,CZCV/s-dilation-caffe,CZCV/s-dilation-caffe,longjon/caffe,gogartom/caffe-textmaps,gnina/gnina