Create a program that asks the user
for numbers, until the user enters zero. It then prints the mean,
median, and mode of these numbers. The statistics
module can be used
for the mean and median; however, for the mode, print all those numbers
that have the highest count, even if that entails that you print more
than one number. By definition, for a number to be the mode it must
occur at least twice; so if every number only occurs once, there is no
mode. Hint: Consider using the Counter
class to construct the mode.