Make a TorClientBuilder API.
This is a defensive API choice to protect against the possibility that we'll want to add a bunch of other non-config options in the future.
There are a lot of design choices here, many of them questionable. Please review carefully with a bunch of thought about how this could be done differently.
There are lots of places that examples could be added. Please let me know where you think they could/should go.
Closes #350 (closed)