Replace mail-mode call with compose-mail from GNU Emacs.
This patch is a modified version of the current revno 3323.
It overloads it by:
1. defining a different python class EmacsMail "MUA agnostic".
To use this option, just put these lines into ~/.bazaar/bazaar.conf
[DEFAULT] mail_client = emacsclient
2. supporting any mail client of GNU Emacs family (mail-mode, message-mode, ...) The right tool will be called according to the value of the variable ``mail-user-agent``. So Virtually any Emacs mail client will work transparently if registered against ``mail-user-agent``.
3. adding a wrapper function around MIME attachment. This allow us not to have many different functions/classes to attach a file but one.