Use a remote File Storage system

[Potherca]

To be able to run this on Heroku we need to move file storage away from the local file system and into some external file storage. The Amazon Web Services Simple Storage Service (AWS S3) seems a good candidate, although other candidates are also available (RackSpace, Google Cloud, etc. Or we could abuse Dropbox/Copy.com style services).

The easiest way to implement this would be to refactor the code to use the FlySystem local adapter and when this works, switch over to the AWS S3 adapter. This would also make development easier as we could make the adapter configurable. (We wouldn't want to use up our entire free quota just debugging, now would we?)

If an other service provider seems more attractive than AWS we could create an adapter for it.

[Potherca]

Eventually it might be nice to allow end-users the means of saving stuff to a service of their choice.
This needs to be taken into account when implementing this.