add support for configurable wrapper

[erwinsmit]

Hi,

Love this library, I've been using it across a couple of projects.

One thing that would make it a bit more flexible is to add a configurable wrapper element. This allows this library to be used in navigations for example (so a "<\li>" is used instead of a "<\div>").

Please let me know if you think this is a good addition. If so, I'm happy to have a look at the tests which are currently failing because of this change.

[erwinsmit]

@ethanselzer Is this project still maintained?