Word frequencies should be monotonic.

If you look up a word in the wordlist, and it occurs 0 times, then you
get the default_freq back as your result. If it occurs once, previously
you would get 1. What you should get is (default_freq + 1), so that it's
higher than not being there at all.
Merge branch 'master' of github.com:commonsense/metanl