S3 Storage Backend

[gjtempleton]

Add the ability to use S3 as the storage backend rather than just local disk

[Spedge]

Looks as if afero will give us the option to do this. spf13/afero#90

[Spedge]

I've (finally) merged the new storage layer that was going to use the afero lib so S3 storage should technically be possible once the above merge request is accepted.