Remove boolean return

Instead of returning boolean from the delete_photos! method, returning the response from the API is much more useful.

Author: stmott

lib/spark_api/models/listing.rb

@@ -237,7 +237,6 @@ def respond_to?(method_symbol, include_all=false)
 
       def delete_photos!(photoIds, args={})
         connection.delete subresource_path("photos") + "/#{photoIds}", args
-        true
       end
 
       def delete_photos(photoIds, args={})