* Catch ValueError when parsing datetime strings.
* Map words file contents to lowercase (many fewer false positives).
* Reference options["verbose"] through polly object to allow
  on-the-fly changes.
Add an "add" command. Squawk goodbye on exit.
Flesh things out a bit.
Got this list from the net and culled words containing non-lower-case
characters.
If the corpus is completely empty, initialize it using a random subset
of the given words.
Note how you can cheat.