Description:
	The geocodable migration generator creates a migration which you can use to generate two tables:
	
		geocodes - Contains the latitude and longitude coordinates, with the address they refer to.
		geocodings - The polymorphic join table.
	
	
Example:
    ./script/generate geocodable_migration add_geocodable_tables

    With 4 existing migrations, this will create an AddGeocodableTables migration in the
    file db/migrate/5_add_geocodable_tables.rb