add visualization helpers
fix arbitrary object removal

There were two bugs here

1) when doing a delete_swap we weren't properly setting the first
elements parent

2) when trying to remove an element of the same order as last we were
erroneously trying to swap with that element, instead of putting it in
place of the removal item and then doing a heap-up

fixes #1, tjfontaine/node-dns#33
update example heap.print and cleaner test debug