Updated for seneca 0.5.20, use REQ/REP rather than PUSH/PULL

Changes:
* Use latest seneca-transport
* Change zeromq messaging pattern to REQ/REP (i.e. client/server) rather than PUSH/PULL.
  * Previous implementation was responding to client by client opening a pull socket and the server pushing to it.
  * Pipelining should be provided by seneca - so REQ/REP more suitable than PUSH/PULL
* Use seneca-transport-test standard tests