Plugin does not support translation for singular/plural variations

Hello,
i’ve find out that the plugin miss support for singular/plural variations of translated strings. This kind of variations can be introduced using ngettext() instead of gettext(), or _n() instead of _e().

For example, _n( string $single, string $plural, int $number, string $domain = 'default' )

I think this would be a great improvement for the plugin, and also not necessarily a hard one to implement, as you “just” need to do the same things you are already doing for gettext() & _e() with a slightly different regular expression.

I would have done it myself, but I admit that the current regular expression leaves me a little pensive ^^.