This change is probably going to impact all the other existing parsers where the property was passed as a single string.

May be we can use instead

```ruby
def value_for_property(element, *properties)
   ...
```

and invoke the method as

```
value_for_property(element, 'Fax')
value_for_property(element, 'State', 'State/Province'),
```

or handle the conversion inside allowing properties to be either a string or Array.

I also wonder how many cases where we need an array are currently there. As far as I can see, only State + State/Province, right?