Cover Resize
Resize an image to cover any given dimensions: upscaling, downscaling and cropping when needed!
http://api.rethumb.com/v1/cover/250x150/http://images.rethumb.com/image_coimbra_300x300.jpg
http://api.rethumb.com/v1/cover/250x150/http://images.rethumb.com/image_coimbra_300x300.jpg