Don't call upcase! and preserve original values

[FanaHOVA]

The upcase! call is modifying the params passed to the method call, which can be a pain to debug since it's not a clear result. Example:

> test = 'Alessio'
> CodiceFiscale.calculate(name: test,.... )
// Calculated Value
> test == 'ALESSIO'
true

If this is used in an ActiveRecord validation, the upcase value will be passed along and it will be stored in the database as upcase instead of having its original capitalization. Right now I'm using

CodiceFiscale.calculate(name: name.dup...)

But it seems like an unnecessary thing to do, a library should never change the values I pass to it unless it's a bang method.