version 0.4: minor code changes, debugged database

- The database is built under Python 3.3.2, so it should correctly
  implement Python 3's Unicode tricks, including special handling
  of Greek lowercase letters. (Version 0.3 was supposed to do this
  as well, but apparently, it didn't.)
- `word_frequency` and `iter_wordlist` can be imported from the
  top level.
- The new function `random_words` supplies a string made from
  random words that are sufficiently high in rank order.