Add support for enclosing link in an li tag with active class
Add active_wrapper option to enable active classes on wrapper tags

Adapt's markturner's pull request (https://github.com/robotmay/link_to_active_state/pull/1)
to add support for generic wrapper elements. When present the active state options will be
added to the wrapper element instead of the link.
Merge pull request #2 from robotmay/wrapper_elements

Add support for wrapper elements