Remove an unused bit of code in tree iteration
Set tree->iteration_args back to NULL after iteration is done
Make sure to anchor search for first node in tree when testing
Make $tree->iterate operate in depth-first order when called from Perl

Also added docs for this method.
Require Net::Works 0.20
Merge pull request #11 from maxmind/dave/iterator-is-sorted

Make the iterate method operate in depth-first order when called from Perl