Option to restore terminal when interrupted

[nicollet]

Add option ExitRawOnInterrupt (default off). When turned on, change
disposition of SIGTERM and SIGINT, so that we restore the terminal
mode before exiting. That way, prevents users from having to reset
the terminal themselves most of the time.

[chzyer]

Hi, @nicollet
The current version has a bug that does not restore the terminal when receiving a SIGTERM/SIGINT.
But I think adding an option ExitRawOnInterrupt to the configuration is a bad idea because the configuration is changeable.
I have an implementation for fixing it in #200. You can check if that is what you want.
If not, you can reopen it.