Fog

Simple PR to show how easily aws/s3 could be swapped for Fog.  You can see from my first commit there is a near 1-to-1 correlation.  This code keeps aws support but adds several other cloud storage providers.  See http://fog.io/about/supported_services.html for the current list.

I did not test against live AWS S3, but did test AWS in Fog.mock! mode, and against live Rackspace Cloud Files.

Note: this would make s3cp a misnomer.