Add an option to disable client window resizes

[guywithnose]

This goes great with tmux when you are sharing your terminal for
presentations and you don't want to give viewers the ability to resize
your terminal

[yudai]

Thanks! Merged.

[perguth]

Somehow this does not work on my end. width and height prevent resizing but whatever value I use the output always has the same size (too small in my case / smaller than it was using resizing).