Fix bugs found when released to the wild

- If the location does not contain a 'City' field, make sure the header format is correct.
- If the weather information contains no hourly forecast, make sure to return a useful error message instead of raising an exception.
- If the weather information contains no daily forecast, make sure to return a useful error message instead of raising an exception.
Merge pull request #24 from theckman/non-us_location_bug

Fix bugs found when released to the wild