This is mostly to set us up to test the rpc::Client's reconnect
logic.
There are multiple ways that the `rpc::Client` may establish
its websocket connection: (SSL in production, plain TCP during
local development, and using an in-memory connection for tests).
Now we can represent all of those connections using a common type.
Also, several long methods no longer need to be generic, which
is good for compile time.
Max Brunsfeld
b6eac57f63