net-io

(after #442)

This PR changes net to use `io` instead of channels.
At the moment it's just `conn`, but soon more.
>  It builds but doesnt work yet (or at least i dont think it does).

Silly me. I tried to run it. Panics. At least there's a test in place. https://github.com/jbenet/go-ipfs/pull/461

You really went all out with the interface. Less is more, ya know?