Fix best value

https://www.pivotaltracker.com/n/projects/877197/stories/80351182

Best Value was using two scopes based on priority, others_with_lower_priority and others_with_higher_priority. others_with_lower_priority used used a greater than scope, others_with_higher_priority used a less than scope. but neither includes equals to. This changes to use greater than or equals to scope for others_with_lower_priority, and updates the specs accordingly.
A result of my debugging. I probably didn't need to, because the scoped query would be returned anyway, but thought it was more consistent with the rest of the function.