Move example.jpg inside manga_ocr package

[vaxr]

Fixes #43

Summary

Move assets/example.jpg to manga_ocr/assets/example.jpg, so it can be distributed by setuptools.

Motivation

After installing the manga-ocr-git AUR package on Arch Linux and running the binary, it crashes because it cannot find assets/example.jpg. The linked issue describes a similar experience.

Rationale

• The AUR package uses setup.py install --root to install manga_ocr to the system. The example.jpg file is indeed not included.
• assets/example.jpg is included in MANIFEST.in, but setuptools ignores it, because the assets/ directory is not inside any package configured in setup.py.
• Explored how to include the file without moving it out of assets/ under project root, but haven't found any good solution: The only option I am aware of would be: package_data={ 'manga_ocr': ['../assets/example.jpg'] }. The problem with that is it distributes the assets/ dir right into site-packages/ root, and not under the package namespace.
• example.jpg isn't used anywhere else in the project, so hopefully moving it under manga_ocr/ should be fine.
• Tested manually with local build and pointing AUR at my repo, both work fine.