Allow the Horizon client to use the horizon server directly when running in Node #792
Description
Right now, if you want to use the horizon client in Node, you have to create a websocket to the server no matter what. This is pretty wasteful for things like pre-rendering markup. It would be nice to be able to send Horizon protocol queries directly into the server without having to create an extraneous websocket connection. In addition, we could probably skip serialization/deserialization by passing the protocol objects directly.