total_steps and total_distance for DailySteps should be able to be None

[KopyWasTaken]

When I was pulling some of my data from the API, I was running into errors because I hadn't taken any steps yet for the day I was parsing (it was just past midnight). I think instead of this throwing an error in garth, it should be allowed, because it's a possibility that someone can have taken no steps and traveled no distance in the day yet.

Those values were in fact accurate, and were successfully communicated through the Garmin API, so I don't think it should cause a garth error.