Make a more sane frontend for building a BAPS client.

BapsClient is now the high-level client that can be launched in an
EventMachine process.  The connection level entity is now called
BapsConnection.
Add (nonfunctional) client to server loop.

This will probably turn out to be a bad idea.
Start model bring-up.

Currently the model is empty and not populated, but some query
logic is being added to Sinatra to interrogate it.
Bumper Pak of more model-y additions.

Too much stuff for me to break down into a decent commit message.
Maybe I should commit more often.
Rubocop again, also add channel state callbacks.