Problem with custom field (WooCommerce) – e-mail

Hi,
I know, how to add a custom field to the checkout page in WooCommerce, but it doesn’t sent me e-mails.

Here’s the instruction
http://docs.woothemes.com/document/tutorial-customising-checkout-fields-using-actions-and-filters/

https://gist.github.com/mikejolley/2263203
Someone wrote: The code is not works for WC 2.1.12

What shout I add to receive mails?

Thanks for help.