Add keybindings to the config.
Fix a delay when closing booru tabs.
Use File.write when saving the config file.
Make Booru::Browser#calc_min_width a little less ugly.
Changed StatusBar#set_message and clear_message.  Made ImageBox#scroll, toggle_fullscreen, and toggle_slideshow public.
Minor changes in image.rb
Fix a crash when changing image lists while current image is being
drawn.  Fix @@missing_image in booruimage.
Fix page down, home, and end keybindings for ImageBox.