Add support for TLS connections

See examples/ExampleTLSClient.hs and examples/ExampleTLSServer.hs.

 - Add coUseTLS labeled field to ConnectionOpts

 - Switch from GHC.IO.Handle to Network.Connection

 - Depends on unreleased connection-1.3-dev

 - To build see: https://gist.github.com/AlainODea/7852276