Convert to absolute path
Convert to absolute path

Sometimes `os.path.dirname(__file__)` returns empty and it makes `dataset_dir` empty.
This causes a permission error for most of uses because `save_file` will be created at root path.
To avoid this, we have to convert current file path as absolute path then take its parent directory path.
kgsn1763/deep-learning-from-scratch,oreilly-japan/deep-learning-from-scratch