changing merge to merge!

gistfile1.rb

    require "benchmark"
    N = 1_00_00_000
    Benchmark.bmbm do |x|
      x.report("Indifferent Access") do
        N.times do |i|
          HashWithIndifferentAccess.new(i)
        end
      end
    end

=begin
With merge

Rehearsal ------------------------------------------------------
Indifferent Access   9.570000   0.380000   9.950000 (  9.945525)
--------------------------------------------- total: 9.950000sec

                         user     system      total        real
Indifferent Access   9.580000   0.370000   9.950000 (  9.939738)

With merge!

Rehearsal ------------------------------------------------------
Indifferent Access   7.950000   0.610000   8.560000 (  8.599360)
--------------------------------------------- total: 8.560000sec

                         user     system      total        real
Indifferent Access   7.960000   0.590000   8.550000 (  8.553272)

=end