changes to implement timeouts with non-blocking reads and writes

[jwedoff]

This work I did to finish read/write timeouts using non-blocking reads. (partially addressing issue#247?) I've used it successfully in production for some custom services, but I couldn't figure out how to sensibly test the new functionality with the existing testing framework. We'd love to get our changes upstreamed, and I'd love to know if you have any ideas of how to go about testing.