Model method to normalize input values

I'd like to have a class method such as `normalize_values` that does something like this:

```
input = {product_code: "  ABC123  "}
clean_input = Product.normalize_values(input)
#=> {product_code: "ABC123"}
Product.where(clean_input)
```

This would effectively build a new model instance to push values through the normalizer, and read them back. Is that within scope of your gem for a pull request?
