Currently, the preferred way of contributing code to the project is through the project's GitHub page. You can create a fork of the project under your own repositories and start working from there. When you believe you have finished and would like to send your contributions to the project, please create a pull request so the project maintainers can review and hopefully accept incorporating your code into the main branch.
Despite being the preferred venue for sharing contributions, the project will always be open to suggestions and will never recriminate if you chose to share your code another way - such as sending them over by email, like most of the contributions we received over the years. But if you can, please try to share it through GitHub with us! Unfortunately, email is far too easy to miss, specially in a crowded inbox.