call binmode on the tempfile for Ruby 1.8 compatibility

Author: tenderlove

activesupport/lib/active_support/core_ext/file/atomic.rb

@@ -16,7 +16,8 @@ def self.atomic_write(file_name, temp_dir = Dir.tmpdir)
     require 'tempfile' unless defined?(Tempfile)
     require 'fileutils' unless defined?(FileUtils)
 
-    temp_file = Tempfile.new(basename(file_name), temp_dir, :binmode => true)
+    temp_file = Tempfile.new(basename(file_name), temp_dir)
+    temp_file.binmode
     yield temp_file
     temp_file.close