Added support for 'nearest' and 'locate' queries

Addresses issues #52 and #44.

You might make an argument for having a `Query` base class with `RoutingQuery`, `NearestQuery`, and `LocateQuery` sub-classes, but this just seems like overkill... Opted for a simple addition of a "if this is a 'nearest' or 'locate' query" conditional block to the existing `Query` class.

Hoping we can move forward with this for now.