Use datapackage-rb gem to infer and generate datapackage.json from transformed data

[switzersc]

Right now we do not dynamically generate the datapackage.json file based on the contents of the transformed data directory, but we should. This is because transformed data may not include all HSDS models or fields, and may include additional custom fields, so using a static datapackage.json file would not be capture these idiosyncrasies. We want to use the datapackage-rb gem to do this, but this feature is not supported yet so is dependent on a PR to that gem to add the functionality. Once that's done, we can utilize the gem here to create the JSON file.