Move to trash sound not working [Fix coming soon]

On Lion, the move to trash.aif file is at:

```
/System/Library/Components/CoreAudio.component/Contents/SharedSupport/SystemSounds/dock/drag to trash.aif
```

I guess we just need to add an `isLion` method then alter the path accordingly.

@HenningJ - would you be able to do this, since it was your fix?
