masciugo/genealogy — pull request #3 by mjc (2014-08-03 04:32:48+00:00)
Title: if self.offspring returns nil, incompatible_parents shouldn't be boolean

With 3 items and no genealogy set up, trying to call .add_father or .add_parents bails because:
```
nil | [] | [self]
```
evaluates to true.

this patch fixes this.