Add .builds() with some caveats:

spray-json currently only allows case classes that have 15 or less parameters.
There's one workaround, but it means defining our own JSONFormatter, which is
a bit annoying.

Instead, I trimmed out several fields from the response (mostly _id fields and
left their string equivalents) in the case class.

This problem is fixed in spray-json2, where it will let us have case classes
with up to 22 parameters (like the Scala stdlib), but that's not released yet.

For the time being, I think this is a good middle ground without losing any
really important information. Still, this limitation is a bit annoying. :(