Get all tests to passing state.

A few things in this PR:

0. All tests pass. Yay!

1. Pattern matching with bitstrings has apparently changed in the last few months, and it is very poorly documented, afaict. The function `decode_binary(<<?:, tail :: binary>>, acc)` required a lot of research. I finally wound up at [this](https://github.com/elixir-lang/elixir/issues/1437#issuecomment-21083637) thread that explained the issue. I think this is really gross/weird syntax... at least not documented well enough.

2. The `test.torrent` file required encoding as hex, which I guess makes sense since there's probably some cyrillic in there. I added that. I don't know if that will be problem for you.

3. I changed a couple tests to make them easier to inspect with `IO.inspect`.

That's it. Thanks!