made .iso639 source ethnologue/wikipedia

completing [this GCI 2013 task](https://google-melange.appspot.com/gci/task/view/google/gci2013/5869879995400192)
`.iso639 <lg>|<Language>` works as always, except now queries 639-1, -2, and -3.
`.isodb update` scrapes ethnologue and wikipedia for codes and updates the database on the filesystem
`.isodb status` states if the code update task is running (for it takes some time)