Add instructions for exiting Medley

[pamoroso]

To address issue #1332 I added instructions for exiting Medley.

[masinter]

@rmkaplan note it uses il and not li for the default home dir (vs PSEUDOHOSTS).
@fghalasz note that this is patching the current install-and-run instructions if you're working on new ones.

[pamoroso]

Is @fghalasz working on similar changes to these pages?

[pamoroso]

How can we proceed? Should I withdraw or modify this PR?

[masinter]

these changes don't seem to conflict with what I believe @fghalasz is doing to the install instructions.

for myself, I just close the window or type a control-C to the shell terminal where I started medley.