Provide rsync access to the marmalade package repository

[xuchunyang]

To do so will make it easier to mirror the Marmalade elpa. For example, the Emacs-China ELPA mirror [https://github.com/emacs-china/elpa] is downloading all elpa packages through HTTP, however, it is inefficient and fails occasionally.

See also the same request for melpa: https://github.com/melpa/melpa/issues/4020