I don't think Support can copy everything over for you, but someone may correct me or provide an easier solution.
0) Backup all of your mail if you're using IMAP. If you use POP, do one last mail check.
1) Backup the rubylearning.com directory in your friend's account and restore it to your own directory as rubylearning.sav
tar -cvf rubylearning.tar rubylearning.com
2) Backup your database and then copy it into your home directory:
mysqldump -h oldhost -u oldusername -poldpassword olddbname > rubylearning.db
3) Have your friend delete the domain from his account.
4a) Create a Fully Hosted Domain in your own account.
4b) Restore your domain backup
5a) Create a new database for your domain
5b) Restore your database:
mysql -h mysql.example.com -uusername -ppassword newdbname < rubylearning.db
6) Re-create any e-mail addresses you have