added associations to identity map

lib/identity_map/active_record/associations.rb

@@ -0,0 +1,31 @@
+module IdentityMap
+
+  def self.included(base)
+    base.extend(ClassMethods)
+    class << base
+      alias_method_chain :association_instance_set, :identity_map
+    end
+  end
+
+  module ClassMethods
+
+  private
+
+  # Set the specified association instance.
+  def association_instance_set_with_identity_map(name, association)
+    identity_map = Thread.current['identity_map']
+    unless identity_map
+      association_instance_set_without_identity_map("@#{name}", association)
+    else
+      association_instance_set_without_identity_map("@#{name}", identity_map.put(association))
+    end
+  end
+
+
+  end
+
+end
+
+if Object.const_defined?("ActiveRecord")
+  ActiveRecord::Associations.send :include, IdentityMap
+end