Please see the new variable `ein:completion-backend'. Use this variable to
configure which completion backend to use in ein. Currently we support
auto-complete, company-mode, and jedi using auto-complete.
Only six months late. Jupyter changed callback signature for
complete_request, breaking ein's autocomplete code. Missed this for so
long because I am lazy and almost exclusively used jedi for
autocompletion. Ugh.
* Change the call signature of completer callback, to
pass arguments to completer callback.
* Use expand option to suppress auto expansion when
used as dot-complete.
