create person model, create name method
create birthday method for person model
create have_a_drink method and age helper method for person model
update have_a_drink method to include drunk condition
create drive_a_car method for person model
create sober_up method for person model
update have_a_drink method to check for age
update drive_a_car method to check for age
update drive_a_car method to check age
refactor to use relative birthdates