[Tile38] Return both objects' coordinates in roaming geofence events

It'd be really useful if roaming geofences included both objects' position in its JSON; for example, taking the example JSON from the [roaming geofences documentation page](http://tile38.com/topics/roaming-geofences/), something like this: ``` { "command":"set", "detect":"roam", "hook":"", "key":"people", "id":"alice", "time":"2016-05-24T09:19:44.08649461-07:00", "object":{"type":"Point","coordinates":[-115.02,33.02]}, "nearby":{ "key":"people", "id":"bob", "meters":1451.138152186708, + "object":{"type":"Point","coordinates":[-115.01,33.01]} } } ```