MingchangLi

see #32 change `self.criterion = nn.NLLLoss(ignore_index=0)` to `self.criterion = nn.NLLLoss()`

An importance step before running code is to unzip NTCIR-12 dataset and extract all tarballs under the sub-directories by `for x in *.tar.bz2; do echo $x; tar xjf $x; done`

NOTE: If you find the bounding boxes are displaced from math regions, it is because the document image that you have rendered is of different size than the one used...