Completed count_unique, count_unique_bonus, going back to do them with speed
Added common_items2 using for item in list1, then add keys to dictionary, increment repeated keys in list2
Recreate common_items2
Recreate common_items2
Sum_zero not using tuples
sum_zero using dictionary
Include result list in sum_zero
Find duplicates, word_length functions added
Word_length unpack tuples in for loop