Integrate an object storage support

[freyes]

This project will need to store information somewhere, to make the workers where the activities run stateless we would like to make the activities and workflows to pull and push data from some remote storage (e.g. an object storage), but still keep a nice fallback to local disk storage to make development and testing easier.

There is a library called cloudstorage which provides different drivers, but more importantly has a driver for local storage, we could use swift/s3 or local storage with the same API.