Zip is not a function when using a local

[devbyray]

When I set the local to 'nl_NL' the zip is not a function but a property. I think this should be more consistent.

[josher19]

I think this was introduced by this commit / Pull Request: https://github.com/boo1ean/casual/pull/26/files

It should be a property for every locale and should not be a function for any locale,

Instead of having zip(digits) it should have zip, zip5, and zip9 as properties rather than functions for a more consistent interface.

[josher19]

Used zip_short and zip_long instead of zip5 and zip9 (which is specific to the USA).