New actor to resolve the location of tweets

Adds a new LocationResolver actor that is created as a child of the main bot actor. It accepts messages containing requests to determine the latitude/longitude of a user (based on a GeoNames search on the location string in the user's profile) or a tweet (by first checking if it's geotagged, but backing off to a GeoNames search on the user). There's plenty of room for improvement, but the GeoName search works quite well if the user it's trying to locate has a standard location like "Austin, TX" in their profile.

The LocationResolver actor uses a child GeoNames actor to serialize requests to the GeoNames API.