input: Write a python function to count the occurrences of words in a list and return the top n most common words using the Counter class from the collections module.
  assert top_n_words(['Python', 'programming', 'language', 'is', 'powerful', 'and', 'versatile'], 3) == [('Python', 1), ('programming', 1), ('language', 1)]
  assert top_n_words(['apple', 'banana', 'apple', 'orange', 'banana', 'apple'], 2) == [('apple', 3), ('banana', 2)]
  assert top_n_words(['one', 'two', 'three', 'one', 'two', 'one'], 1) == [('one', 3)]
output: from collections import Counter
  
  def top_n_words(word_list, n):
      counter = Counter(word_list)
      return counter.most_common(n)