Change the logging to report the completion function name and have the end2end
tests check for this.
Remove the tests for realtime completion, as it was decided this is not an
important feature and the code is much simpler without it.
I tested everything that I thought was interesting enough to warrant a
test: especially the ability to test multiple parameters deep, as well
as testing :set --cycle and some involved example to make sure
completion actually works and updates in realtime
