Update Spanish translation
Add Farsi translation
Fix test for override_only
Don't return a Country object for a null or empty string

Fixes #47
Update ISO name for Cape Verde (Cabo Verde)
Update Libya flag
Add European Union flag

No, it's not an ISO country but it's in the exceptional reservation list and is a common one people may want.
Refs #45
Update Burma flag
Fix OVERRIDE_ONLY
Small optimizations to country-related lookups.

This is a technically a backwards incompatible change to the
undocumented api, since countries.countries now returns a dict rather
than a list.

Made in response to a comment in #41.
Don't include the country choices in migration operations.
Merge pull request #58 from schinckel/feature/django1.7

Don't include the country choices in migration operations.