Pheme, Custom Classes, and Multi-Dispatch

[Chromatic]

Perhaps I don't understand how :multi works (and I would love to see more
documentation and will even write tests, as I don't think the existing ones
cover all of the cases).

I added a custom Cons class to Pheme, as that's what a Lisp/Scheme needs.
This means that I also need some more logic for is_deeply() to compare two
Cons objects appropriately.

The attached patch is my first attempt. It doesn't work and I'm not sure why.
I don't know if installing is() from Test::More (it's a multi sub) overrides
the multi is() in Pheme::Test. I don't know if dispatch even *gets* to my
custom is() either.

I don't even know if what I'm trying to do should be possible, at least the
way I'm doing it.

I'm stumped and I appreciate any advice, especially from someone who knows how
multi dispatch ought to work in Parrot and someone who knows how the current
system does work.

-- c