Add 3 new methods to Array class which are match_positions, select_index, and reverse_select_index.

Example:
Given
  a = [1, 2, 3, 4, 5, 'cat', 'dog']
  b = [1, 0, 'cat', 4, 6, 8, 'dog']
  c = [0, 2, 4]

- a.match_positions(b)
#=> [true, false, false, true, false, false, true]

- a.select_indexes(c)
#=> [1, 3, 5]

- a.reverse_select_indexes(c)
#=> [2, 4, "cat", "dog"]