Handle server-side terminal size changes

[yuvipanda]

You can use stty on the
commandline to set the width / height of your terminal. Whenever
it is run in terminado, it sends a change event. We should
handle this, and somehow send it through to the client so the
ssh client knows the current terminal size.

change_terminal_size
might be what's useful.

I'm not sure if we even need this at all, though. Low priority!