Always include distance and bearing columns.

This addresses issue #199 and is more directly a response to the
excellent comments from github.com/zetetic on commit 1b658304.

lib/geocoder/stores/active_record.rb

@@ -36,7 +36,10 @@ module Geocoder::Store
           if Geocoder::Calculations.coordinates_present?(latitude, longitude)
             near_scope_options(latitude, longitude, *args)
           else
-            where(false_condition) # no results if no lat/lon given
+            # If no lat/lon given we don't want any results, but we still
+            # need distance and bearing columns so you can add, for example:
+            # .order("distance")
+            select(select_clause(nil, "NULL", "NULL")).where(false_condition)
           end
         }
 
@@ -49,7 +52,9 @@ module Geocoder::Store
         #
         scope :within_bounding_box, lambda{ |bounds|
           sw_lat, sw_lng, ne_lat, ne_lng = bounds.flatten if bounds
-          return where(false_condition) unless sw_lat && sw_lng && ne_lat && ne_lng
+          unless sw_lat && sw_lng && ne_lat && ne_lng
+            return select(select_clause(nil, "NULL", "NULL")).where(false_condition)
+          end
           spans = "#{geocoder_options[:latitude]} BETWEEN #{sw_lat} AND #{ne_lat} AND "
           spans << if sw_lng > ne_lng   # Handle a box that spans 180
             "#{geocoder_options[:longitude]} BETWEEN #{sw_lng} AND 180 OR " +