first crack at emphasizing use as attributes in POD

Toby Inkster pointed out on cpanratings that the documentation doesn't make
much (any) mention of the actual target audience for this dist (object attrs).

This is pretty awkwardly shoe-horned into the main POD, at the moment; I'll
take another gander when I'm sober ;-)

	modified:   lib/List/Objects/WithUtils.pm