Ability to pass an arguments hash to the materialize class method

Firstly, thanks for your great gem!

We're using Faceted in a project that doesn't use a classical ORM that supports methods such as 'where', etc. and thus we call the materialize method straight from our controller, as in:

    Musician.materialize(results)

and want to be also be able to pass in an 'excludes' hash, as you currently allow when simply creating a new presenter. So, we'd like to be able to do something like this:

    Musician.materialize(results, :excludes => [:id])

This pull request allows the passing of such an argument hash.

Thanks!