Fixed bug with DateTimes not having a #to_i method.

lib/paperclip/attachment.rb

@@ -187,7 +187,7 @@ module Paperclip
     # lives in the <attachment>_updated_at attribute of the model.
     def updated_at
       time = instance_read(:updated_at)
-      time && time.to_i
+      time && time.to_f.to_i
     end
 
     # Paths and URLs can have a number of variables interpolated into them

test/attachment_test.rb

@@ -531,9 +531,10 @@ class AttachmentTest < Test::Unit::TestCase
         @attachment.stubs(:instance_read).with(:file_name).returns("5k.png")
         @attachment.stubs(:instance_read).with(:content_type).returns("image/png")
         @attachment.stubs(:instance_read).with(:file_size).returns(12345)
-        now = Time.now
-        Time.stubs(:now).returns(now)
-        @attachment.stubs(:instance_read).with(:updated_at).returns(Time.now)
+        dtnow = DateTime.now
+        @now = Time.now
+        Time.stubs(:now).returns(@now)
+        @attachment.stubs(:instance_read).with(:updated_at).returns(dtnow)
       end
 
       should "return a correct url even if the file does not exist" do
@@ -542,11 +543,11 @@ class AttachmentTest < Test::Unit::TestCase
       end
 
       should "make sure the updated_at mtime is in the url if it is defined" do
-        assert_match %r{#{Time.now.to_i}$}, @attachment.url(:blah)
+        assert_match %r{#{@now.to_i}$}, @attachment.url(:blah)
       end
 
       should "make sure the updated_at mtime is NOT in the url if false is passed to the url method" do
-        assert_no_match %r{#{Time.now.to_i}$}, @attachment.url(:blah, false)
+        assert_no_match %r{#{@now.to_i}$}, @attachment.url(:blah, false)
       end
 
       context "with the updated_at field removed" do