Entry fallback translation

Without this isn't possible to translate the default "entry name"
When using AR, isn't it better to do something like:

    entry_name = collection.model_name.human(count: collection.total_count).downcase

And not use `.pluralize`? This way it uses the plural/singular translations for AR and does not mess up when the language is not english.

Example:
When I have a model called `Article` it is translated to Swedish like this in my local file:

    sv:
      activerecord:
        article:
          one: Artikel
          other: Artiklar

Kaminari picks the `Artikel` translation and pluralizes it to `Artikels` which is wrong.

If we use:

    entry_name = collection.model_name.human(count: collection.total_count).downcase

It will instead pick the correct plural version of the word.

If we want to be backwards compatible and avoid `translation missing` errors, we can do something like this:

    entry_name = collection.model_name.human(count: collection.total_count, default: c.model_name.human.pluralize).downcase


What do you think about that?