Resolve #1298

* use serial.load in CIFAR10._unpickle
* remove "scripts/tutorials/grbm_smd/make_dataset.py" from pep8 whitelist
* refine serial.load for interoparability between Python 2 and 3
* remove N and np, aliases of numpy
Without `encoding='latin-1'`, PY3 cannot load PY2 pickle. I agree to moving `pickle_load` to `serial` module.