Merges an array of arrays by adding the elements together.

merge_tuples.rb

    # Takes an array of totals_tuples and combines them into a single tuple.
    def self.merge_tuples(tuples)
      tuples.inject([]) do |xs, ys|
        l = [xs.length, ys.length].max
        zs = []
        l.times.each do |i|
          zs[i] = (xs[i] || 0) + (ys[i] || 0)
        end
        zs
      end
    end