Global option for disabling remote validation

As mentioned (https://github.com/guillaumepotier/Parsley.js/issues/143), `data-remote` on a form tag will break Rails' jquery_ujs support for ajax forms. I like @mekishizufu's suggestion of adding a namespace option to the `data-*` attributes to prevent conflicts like this (https://github.com/guillaumepotier/Parsley.js/issues/143#issuecomment-20692481), but this is a unobtrusive workaround in the meantime if remote validation is not needed.