Expose metadata

This passes along a `Map[String, String]`, allowing you to pull anything you need out of the metadata key coming from the fronts api `JSON`.

@ironsidevsquincy Has mentioned that there is no way to retrieve the original headline. This is intentional, as the object `ContentWithMetadata` is only used in the `Facia` project. If and when we need it, we can easily add it to `Trail`.