pillow support

Hey there! I tried to add consistent Pillow support, because I wasn't that easily able to install PIL without pillow. The following two changes would add full pillow support to your project. I don't understand the way it is supported now:
* setup.py
* src/wallpapoz

use Image, but
* src/wallpapoz_gui/wallpapoz_menu.py
* src/wallpapoz_gui/wallpapoz_menu_commands.py

use PIL.Image (the pillow package)..
Regards!