Detect non-tty master operation & act accordingly

When not running on a TTY, don't attempt to clear the tty region that
the zeus master would expect to be clear-able. Also, don't redraw the
status chart in a loop, and timestamp updates so folks can tell when
the last update occurred.
Merge pull request #260 from antifuchs/be-friendly-to-non-ttys

Detect non-tty master operation & act accordingly