Update compass.py
Update compass.py

fix "global name is not defined" error in AndroidCompass.__init__()
kostyll/plyer,kostyll/plyer,kivy/plyer,KeyWeeUsr/plyer,johnbolia/plyer,cleett/plyer,KeyWeeUsr/plyer,kived/plyer,kivy/plyer,kived/plyer,johnbolia/plyer,kivy/plyer,KeyWeeUsr/plyer,cleett/plyer