Install kivy-ios deps after cloning the repo

[meow464]

Reads the dependencies from kivy-ios/setup.cfg (an ini file) and installs them with pip.

With this change the user should be able to just do buildozer init && buildozer ios debug|release and kivy-ios will be automatically downloaded and built. No need to install dependencies.

This is possible since: https://github.com/kivy/kivy-ios/pull/638