change in arborescence -> tensorflow_ + add nystrom_layer in tensorflow_

skluc/examples/fc_nn.py

skluc/examples/fc_nn_cifar.py

skluc/examples/fc_nn_timed.py

skluc/examples/tfrecord_nn.py

skluc/tensorflow/kernel_approximation/__init__.py

skluc/tensorflow_/__init__.py

skluc/tensorflow_/kernel_approximation/__init__.py

skluc/tensorflow_/kernel_approximation/fastfood_layer.py

skluc/tensorflow_/kernel_approximation/nystrom_layer.py

skluc/tensorflow_/utils.py