Add auto-downloader and installer for dependencies

[NeoMahler]

Specially for Windows users (and macOS?) installing dependencies is a hell if they are non-programmers. It should be more or less easy to download the tar.gz file, descompress it and run python setup.py install. Maybe it could be distributed in a separate repo.

Added it for v3.0; I think it's an important issue.

[F4b1-]

Talking about an easier way to get granota running: Uploading it to Pypi might also be a good idea.

[NeoMahler]

Oh! That's true, I should have thought about that before. I will take a look at it when I have time.