Add tests

Redo of https://github.com/turn/ttorrent/pull/61 which was a redo of https://github.com/turn/ttorrent/pull/58 which is all ultimately a cleaned up https://github.com/turn/ttorrent/pull/46.  This time eliminating all changed files, and including only new files in order to make the history clean without requiring a rebase before merging.  If this doesn't do it, I'm out of ideas.