ENH: iohub process and client connection updates

+ Added enableRealTimePriority  and disableRealTimePriority methods to
ioHubConnection class

+ ioHubConnection should now be using a standard python socket to
connect to the iohub server. It was using a gevent socket, which was
unnecessary, and caused issues when ioHubConnection instance was created
in main thread and events were accessed in another thread.