Updated #arrange to use ActiveSupport::OrderedHash so ordering also w…

…orks in Ruby 1.8.

lib/ancestry/class_methods.rb

@@ -36,7 +36,7 @@ def arrange options = {}
           self.base_class.ordered_by_ancestry_and options.delete(:order)
         end
       # Get all nodes ordered by ancestry and start sorting them into an empty hash
-      scope.all(options).inject({}) do |arranged_nodes, node|
+      scope.all(options).inject(ActiveSupport::OrderedHash.new) do |arranged_nodes, node|
         # Find the insertion point for that node by going through its ancestors
         node.ancestor_ids.inject(arranged_nodes) do |insertion_point, ancestor_id|
           insertion_point.each do |parent, children|