automatic locations

Creates a command that generates locations object for locations with many entries. 
* Neighbor class takes an object with coordinates. Finds other objects with nearby coordinates.
* WebFinder finds uses the Neighbor class to find groups of entries (or any object with coordinates) that  are close to each other.
* CoordinateCenter finds the average latitude and longitude in those groups.
* Csv maker formats a file of world cities.
* LocationFinder takes the coordinate centers and the list of cities.  It finds cities that are near those centers.
* LocationBuilder builds new Active Record Locations for each city that Location Finder finds.
There is actually a Ruby `Set` class that implements all of this functionality. 

http://ruby-doc.org/stdlib-1.9.3/libdoc/set/rdoc/Set.html