TODO

• Convert tests to Contest
• Add preprocessing of derivatives as a default, on-the-fly as an option intended only for prototyping
• Test that processors always run in the order specified (probably requires an ordered hash)
• Fix up mime-type recognition for disk/S3 (uses mimetype-fu if available)
• Write tests for S3
• Write tests to verify atomicity of saving/processing (cleanup on failure, etc...)
• Add more tests for S3
• Identify & raise on all failure points (i.e. make sure system calls returned success, etc...)
• Add rake task for re-processing derivatives
• Fix missing column raises when installing plugin and migrating changes to underlying table
• Don't require right_aws unless you use S3
• Break out storing from processing of derivatives, process all then store