BathroomsController#encode_search cleanup

Cleaned up encode_search a bit.

The cases where the `search` parameter is specified, but either (or both) of `lat` and `long` are not specified, is not handled because this would need to be client-side, given how lat/long are being handled. That will be a separate PR. This one should handle all of the other variants of parameters being specified or not specified, however.