Encrypted backend

[troy]

Guys, this might be useful somewhere. It:

• defaults to using the encrypted backend. That default is mentioned but doesn't seem to happen.
• documents the basics of using it
• raises an exception when a nonexistent backend name is used

Edit or ignore as you see fit. Cheers,

Troy

[troy]

Hey Rick, I'm going through old repos and found this pull request. I think this should merge pretty easily - it's forked off the most recent commit in your repo.