Updates converter for ilsvrc2012 dataset
Updates converter for ilsvrc2012 dataset

Major changes compare to ilsvrc2010 converter:
1) Devkit no longer contains 'cost_matrix' in meta.mat file.
2) Test_groundtruth is not available. I use manual counting to get
   number of test examples.
3) Patching images is not necessary.

Note: due to aforementioned changes reusing code is problematic.

dmitriy-serdyuk/fuel,dmitriy-serdyuk/fuel,mila-udem/fuel,vdumoulin/fuel,mila-udem/fuel,vdumoulin/fuel