Support for color pictures

[simonzhaoms]

Actually, you can ml score AColorPicture, internally it will be converted to a grayscale black-white picture. So it it better to demonstrate the original color picture, the grayscale one and the colorized results in a row together, instead of only showing the balck-white and results without the orignal color picture.

[boulaziz]

I am getting the following error:
./.local/bin/ml color colorize --interactive Six_chefs.png
Traceback (most recent call last):
File "./.local/bin/ml", line 11, in
sys.exit(main())
File "/home/khaled/.local/lib/python3.6/site-packages/mlhub/init.py", line 197, in main
args.func(args)
File "/home/khaled/.local/lib/python3.6/site-packages/mlhub/commands.py", line 1061, in dispatch
errors = errors.decode("utf-8")
AttributeError: 'NoneType' object has no attribute 'decode'

[gjwgit]

This issue is about colouring coloured photos and not for new issues with the package. Moved to #6.