fix usage of decrypted bytescale

[alanlivio]

The func scipy.misc.bytescale become decrypted as can see here.
The PR follow this suggestion and use skimage.util.img_as_ubyte with same functionality in some notebooks.

[alanlivio]

what do you think @leandromoreira?

[leandromoreira]

Thanks @alanlivio did you try to run it using the provided docker?

[alanlivio]

Hi @leandromoreira, I ran and the patch worked both inside the provided docker and outside the docker (directly from most recent python and pkgs). Without the patch it doesn't works outside the docker.