fix issue #461

I've fixed this issue using the hash returned by `I18n.t("number.format")`. This hash contains the delimiter and separator characters for current locale. Throught this hash I've modified the `ClientSideValidations.patterns.numericality` in the view, so the regexp can change dinamically depending on current locale.

The user can choose to enable or disable this feature by setting the variable `Config.number_format_with_locale` in the initializer.