- replaced Gtk.HBox/Gtk.VBox by GtkBox as seen in [1] and [2]
GtkHbox and GtkVBox are deprecated
- use delete-event instead of destroy event in GtkWindow
- replaced icon_size for pixel_size where used
it's also deprecated as seen in commit [3]
- use sugar_theme in all examples; set it manually not by just
importing common module
- fixed GtkBox.pack_start arguments
- flake/pep8 fixes
[1] https://developer.gnome.org/gtk3/stable/GtkHBox.html
[2] https://developer.gnome.org/gtk3/stable/GtkVBox.html
[3] 5802d67ee1
