Improvements per https://github.com/FHPythonUtils/Waifu2x/pull/4, thanks
https://github.com/ArielMAJ for the improvements and the changelog :)
- Old `main` function is now called `run` and receives all the same arguments as expected from CLI with the same default values.
- This means the user can now import `waifu2x` and just run `waifu2x.run(input_img_path="./input.png", output_img_path="./output.png")` to upscale images from a script.
- This also means everything works the same (main function calls `run()` with default args).
- Added extra argument to `run` and a few other functions in `__init__.py` as to stop prints from happening (as they might not be wanted when importing this module.
Fix Pillow deprecations https://pillow.readthedocs.io/en/stable/deprecations.html#constants