Support HTTP Transport

[gruis]

Based on changes in 77c5848 both the client and server support JSON encoding the communication payload. It should be possible to take the payload and include it in an HTTP request/response. User auth and session management would have to be modified/written to deal with an HTTP transport, but it's doable.

The utility of this is questionable, but it would allow for a single EM-based web server to provide access to a Pry session even when it is behind a proxy, etc.,.