Implement truncated country names

This implements the compromise described in https://github.com/SmileyChris/django-countries/issues/60

It has issues, though--specifically, listing two Koreas and two Congos. I'd still rather Taiwan just be made an exception, but I can see why others would rather not do it that way.

I could not test this beyond self-generating data.py because I do not have django installed; sorry about that.