@ in image filenames

I hate to be 'that guy' who files bugs like this, but would you mind renaming your image file with an @ in it?

Sadly, google appengine doesn't allow files with an @ in them and sends off this error whenever I deploy:

```
SEVERE: Invalid character in filename: js/leaflet/images/marker-icon@2x.png
```

I could do it myself, but I'd rather not maintain a separate fork and this is an easy fix.
