Add a test for Query.filter(foo__in=[list_of_Objects])

It currently fails because:
  TypeError: <Game:XKz5Hfyxqw> is not JSON serializable
Make Query.filter(foo__in=[list_of_Objects]) work

Basically, if we're asked to convert_to_parse a list, do it for
everything in the list and return the list.

All of the tests pass now, so I don't believe anything has been harmed
in this change.