Add benchmark for allocating 40k objects with + without oink:

                     user     system      total        real
40,000 empty iterations  0.000000   0.000000   0.000000 (  0.002370)
without instance type counter - instantiating 40,000 objects  0.910000   0.020000   0.930000 (  0.922722)
with instance type counter - instating 40,000 objects  2.620000   0.070000   2.690000 (  2.700390)

benchmark/instance_counter_performance.rb

@@ -0,0 +1,39 @@
+#!/usr/bin/env ruby
+
+require 'benchmark'
+require 'active_record'
+require 'sqlite3'
+require File.dirname(__FILE__) + "/../lib/oink.rb"
+require File.dirname(__FILE__) + "/../init"
+
+ActiveRecord::Base.establish_connection :adapter => 'sqlite3', :database  => ':memory:'
+ActiveRecord::Migration.verbose = false
+
+ActiveRecord::Schema.define do
+  create_table :users, :force => true do |t|
+    t.timestamps
+  end
+end
+
+class User < ActiveRecord::Base
+end
+
+Benchmark.bm(15) do |x|
+  x.report "40,000 empty iterations" do
+    40_000.times {}
+  end
+
+  x.report "without instance type counter - instantiating 40,000 objects" do
+    40_000.times do
+      User.new
+    end
+  end
+
+  x.report "with instance type counter - instating 40,000 objects" do
+    ActiveRecord::Base.send(:include, Oink::OinkInstanceTypeCounterInstanceMethods)
+
+    40_000.times do
+      User.new
+    end
+  end
+end