Bugs:
- shouldn't probably steal focus from the nautilus window when open ?
- error handling from plugins should be catched and a fail-whale of
  some sort be displayed
- album arts not square should be canvased into a square shape

Low-priority bugs:
- videos over remote mounts should have some some sort of buffering

Ideas (to be validated):
- make preview window resizable, and save per-file preview size
  in gvfs metadata
- save/share cover art with Rhythmbox/Banshee?
- add a zoom-in/zoom-out effect when opening/closing
