batch :http://www.zhihu.com/question/32673260
caffe blog： http://blog.csdn.net/abcjennifer/article/details/46424949
python: https://github.com/BVLC/caffe/pull/1733
python:https://github.com/tnarihi/tnarihi-caffe-helper/blob/master/python/caffe_helper/layers/data_layers.py