Config to work against fake-s3

[jogaco]

Wanted to simulate s3 for feature tests: https://github.com/jubos/fake-s3

I've had to debug the code to arrive to this config. Might be useful to place in the README.

    datastore :s3,
              bucket_name: '',
              access_key_id: 'myaccess',
              region: 'eu-west-1',
              secret_access_key: 'mysecret',
              fog_storage_options: {
                  host: '127.0.0.1',
                  port: 4567,
                  scheme: 'http'
              }