Check empty source when adding claim

fix the rspec cases and add checking for the source when adding claim
Biggest problem:

This looks to me like it would break if I did this:

```
c = Card['myclaim']
c.name = 'the alley cat is awesome'
c.save!
```

You can confirm that by trying to rename a claim.

It's an existing claim, but I'm not adding any '+source' field; it's already there.