test
Calculates self.distance, representing the user's distance from the screen in mm
Calculates features related to the distance from the screen
Added code necessary to calculate distance from screen features; fixed an error in which some features were named "total_tans_to" and "total_tans_from" rather than "total_trans_to" and "total_trans_from". Fixed some indentation issues.
Changed name of feature to stddevdistance