Replace the country table with a static XML countries file

Storing the countries in the database is overkill, so just use a
copy of the geonames countryInfo data that is loaded into a hash
the first time it is used.

db/migrate/20140117185510_drop_countries.rb

@@ -0,0 +1,5 @@
+class DropCountries < ActiveRecord::Migration
+  def change
+    drop_table :countries
+  end
+end