Remove geoip downloading from setup.py script

While adding support for installing ooniprobe via homebrew I realised that the setup.py has some issues, namely that it tries to write to /usr/share, while in the case of homebrew it should be respecting what is passed via the --prefix command line option.

To overcome this limitation I have refactored heavily the setup.py script and have resorted to delegating the download of inputs to the ooniresources script.