Mask is not rotated and potentially gives errors when rotate and mask are both specified

[abetusk]

I get the following error when trying to use the mask on a rotated pixel sort image:

$ python3 pixelsort.py examples/image.jpg -i random -a 120 -c 20 -m examples/mask.png 
Traceback (most recent call last):
  File "pixelsort.py", line 81, in <module>
    main(parse_args())
  File "pixelsort.py", line 33, in main
    pixels = get_pixels(data, mask, input_img.size)
  File "pixelsort.py", line 62, in get_pixels
    if not (mask and mask[x, y] == constants.black_pixel):
IndexError: image index out of range

After adding the following line:

    mask = Image.open(args["mask"]).convert('RGBA').rotate(args["angle"], expand=True).load() if args["mask"] else None

I get the following image as I would expect:

I'll submit a PR with the fix unless you get to it before I do.

[satyarth]

fixed in 3444f60