Auto merge of #2339 - pnkfelix:downgrade-term-crate-for-emacs-shell, r=alexcrichton

Downgrade term crate back down to 0.2 (from 0.4).

This is undoing part of commit dd34296

Fix #2338

(Unfortunately I do not have a suggestion for how to make a unit test for this problem; doing so would require putting in a bit more effort than I have time for at the moment.)