Stabilize order of records in YAML files

Without this PR, some databases cause generated fixtures to appear in arbitrary order, which creates large diffs upon
minor modifications to the fixture structure.

lib/fixture_builder/builder.rb

@@ -99,7 +99,7 @@ def dump_tables
           table_klass = table_name.classify.constantize rescue nil
           if table_klass && table_klass < ActiveRecord::Base
             rows = table_klass.unscoped do
-              table_klass.all.collect do |obj|
+              table_klass.order(:id).all.collect do |obj|
                 attrs = obj.attributes.select { |attr_name| table_klass.column_names.include?(attr_name) }
                 attrs.inject({}) do |hash, (attr_name, value)|
                   hash[attr_name] = serialized_value_if_needed(table_klass, attr_name, value)