FIX: keep the "uploading..." indicator until the server replies via the MessageBus
FIX: text was disapearing when uploading an avatar
PERF: always use a region for S3 (defaults to 'us-east-1')
FEATURE: ApplyCDN middleware when using S3
FIX: use the same pattern to store files on S3 and locally
PERF: keep a local cache of uploads when generating thumbnails
FEATURE: migrate_to_s3 rake task
