notify_dbus replace previous notification with the same title

On linux, when using the dbus notification library, is possible to override the last notification in order to not have many notifications from the same user,
I have a propose that looks at the current summary/title of the notifications, and following notifications with the same title are overridden, for example when receiving 3 notifications like:
PM from me:  "hello"
PM from me: "world"
PM from you: "!"

only two of them are displayed in the notification area, in particular those are shown:

PM from me: "world"
PM from you: "!"

this avoids notifications floods, what do you think?
ps (this pull request should be reviewed also with https://github.com/guyzmo/notossh/pull/9 because there the order of the title and body is inverted, line 116 )

thanks!