Normalize paths.
Use save_image from pilkit to avoid reinventing the wheel.
Move to pilkit.

Replace the custom code in the image module by pilkit generators.
Copy the original image if needed.
Handle exception when PIL fails to read EXIF metadata
Merge branch 'pilkit'
Remove multiprocessing.

Because it does not work correctly and makes it harder to debug the image
operations. Will see later how to put it back.
Fix a test with generate_thumbnail