Add timeout blocks to Socket/ZMQ send_request

Bump the default timeout to 300 seconds since we haven't been operating
with timeouts in the socket and zmq layers.
Add timeout_wrap to rpc connectors common module

Use timeout_wrap in socket/zmq connectors to get the same behavior and
error handling regarding timeouts.
update zmq server to use router-router for true parallel execution
Merge pull request #59 from localshred/timeouts

Add timeout blocks to Socket/ZMQ send_request
Bump version 2.6.6
Merge pull request #60 from localshred/bdewitt/zmq_lb_broker

Update zmq server to use router-router for true parallel execution
Remove socket close ensure in socket connector
Bump version 2.7.0.rc1