Fix OrderedHash.select to return self instance.

On ruby 2.1.1 the behavior of .select and .reject has changed.
They will return a Hash new instance, so we need to override them to
keep the instance object class.

activesupport/lib/active_support/ordered_hash.rb

@@ -28,6 +28,10 @@ def encode_with(coder)
       coder.represent_seq '!omap', map { |k,v| { k => v } }
     end
 
+    def select(*args, &block)
+      dup.tap { |hash| hash.select!(*args, &block) }
+    end
+
     def reject(*args, &block)
       dup.tap { |hash| hash.reject!(*args, &block)}
     end

activesupport/test/ordered_hash_test.rb

@@ -120,7 +120,9 @@ def test_find_all
   end
 
   def test_select
-    assert_equal @keys, @ordered_hash.select { true }.map(&:first)
+    new_ordered_hash = @ordered_hash.select { true }
+    assert_equal @keys, new_ordered_hash.map(&:first)
+    assert_instance_of ActiveSupport::OrderedHash, new_ordered_hash
   end
 
   def test_delete_if
@@ -143,6 +145,7 @@ def test_reject
     assert_equal copy, @ordered_hash
     assert !new_ordered_hash.keys.include?('pink')
     assert @ordered_hash.keys.include?('pink')
+    assert_instance_of ActiveSupport::OrderedHash, new_ordered_hash
   end
 
   def test_clear