Update lib/apn_on_rails/app/models/apn/group_notification.rb

fix for rails 3 utf8 issue (combining US-ASCII string with UTF-8 string)

lib/apn_on_rails/app/models/apn/group_notification.rb

@@ -72,7 +72,7 @@ def to_apple_json
   # Creates the binary message needed to send to Apple.
   def message_for_sending(device)
     json = self.to_apple_json.gsub(/\\u([0-9a-z]{4})/) {|s| [$1.to_i(16)].pack("U")} # This will create non encoded string. Otherwise the string is encoded from utf8 to ascii with unicode representation (i.e. \\u05d2)
-    message = "\0\0 #{device.to_hexa}\0#{json.length.chr}#{json}"
+    message = "\0\0 #{device.to_hexa}\0".force_encoding("UTF-8") + "#{json.length.chr}#{json}".force_encoding("UTF-8")
     raise APN::Errors::ExceededMessageSizeError.new(message) if message.size.to_i > 256
     message
   end