Scrap unused Twemproxy config files

* Upstream refers to itself inconsistently as Twemproxy or Nutcracker. We've
  standardized on Nutcracker.
* The Nutcracker configs are managed by Puppet, so get rid of the dupes in this
  repo.
* Don't keep the non-Nutcracker setup in a comment. Someone will inevitably
  forget to update it and it will become gradually more dangerous. For better
  or worse, we rely on Nutcracker now. Turning it off will require more than
  uncommenting a few lines.

Change-Id: I812c0bb6cc121d9df58a3eedb14e387507445ee6