setup: proper setup.py: setup.py is working, but there is two issues with Kivy: cython need to be installed first, and stable version currently doesn't work with most recent cython (cf. https://github.com/kivy/kivy/issues/5375 and https://github.com/kivy/kivy/issues/5606). A requirements.txt has been added to use dev version of sat + dev version of kivy which works with latest cython. Once cython is installed, pip install -r requirements.txt works fine.