Adds retina image support to bfi_thumb.
Instead of creating a single image e.g. your_image.jpg, you'll get a second image called firstname.lastname@example.org which is double the size. This gives it compatibility with WP Retina 2x http://apps.meow.fr/wp-retina-2x/
You can change the '@2x' suffix to something different if you prefer.
See the original project here: https://github.com/bfintal/bfi_thumb