File's name retrieval in demo.py not compatible with Windows

[claudio-bon]

Instead of retrieving the file's name in this way:

RAFT-Stereo/demo.py

Line 47 in f1fa15a

file_stem = imfile1.split('/')[-2]

doing it like this:

file_stem = os.path.splitext(os.path.basename(imfile1))[0]

provides compatibility with Windows as well.
Mind that

import os

must be added.

[lahavlipson]

Thanks for pointing this out, I didn't realize there was incompatibility. I'll update the source code