Fix: schema_dumper.rb stops on schema errors

I've got message "# Could not dump table "places_groups" because of following StandardError" because I use enum types in DB. In PostgreSQL it is custom type. ActiveRecord (activerecord (3.2.9)) cannot dump it and send this message.
It is normal for me.
But migration_comments gem stops rake:db:migrate if schema file contains error message (starting with '#').
This fix will tell schema_dumper.tb to ignore error messages.