Matplotlib backend using a notebook in Gtk3

While the work on MEP27 matplotlib/matplotlib#4143 is merged and the work on MEP23 (Multi Figure Manager) is done this little project allows to use a Notebook to hold several figures.

To run it needs Matplotlib Master and for the moment it is only available for GTK3 If you have any problems, questions or suggestions just let me know (issues, PRs)

Take a look at https://github.com/fariza/tabbed_backend/blob/master/example.py for a simple example