Calculate Gradient function does not take in the use_gpu flag

[vinayshekharcmu]

Calculate Gradient function does not take in the use_gpu flag. Although the flag is taken in the visualize function, it is not used in the calculate_graidents function

[vinayshekharcmu]

I have a PR ready. But don't have permission to push to the repo.

[MisaOgura]

Hi @vinayshekharcmu,

The calculate_gradient (for the Backprop class) does take use_gpu flag.

However, I spotted that visualize function does not pass that flag down to the underlying calculate_gradient function.

Will release this fix very soon.

Many thanks,
Misa