Wizard using ncurses should not exit without user input

[ezyang]

Steps to reproduce: Do a Scripts installation on Linerva using 'athrun scripts'

Expected behavior: A success message saying your Wizard has been installed at some location.

Actual behavior: The screen is cleared and all you see is 'Connection to scripts.mit.edu closed', no indication of success.

Reason: Some shells will clear the screen upon logout. This means that a message that we painted to the screen using ncurses gets wiped. If we ask the user to press a key before exiting, they will be able to see the message.