Un-hard-code thousands delimiter.

The delimiter was being set to '.' when formatting some numbers. This caused the result to look strange in the en locale. I removed the optional :delimiter argument to number_with_delimiter, which causes that helper to default to the locale.

The old behaviour can be restored by setting your locale's number/format/delimiter to '.'. See https://github.com/svenfuchs/rails-i18n/blob/master/rails/locale/de.yml for example.