Setting input_subtract and input_divide in bob.learn.mlp.Machine

Created by: ivana7c

The PyNumber_Check seems to pass also for numpy.array, and returns an error when you try to use this setter with numpy.array:

https://github.com/bioidiap/bob.learn.mlp/blob/master/bob/learn/mlp/machine.cpp#L438

The same applies for the input_divide setter.